JPH05101315A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide a magnetic recording and reproducing device capable of correctly reproducing information in the case of that the amplitude of reproduced waveform is asymmetry in upper and lower parts as when a MR head is used in magnetic recording and reproducing, as well. CONSTITUTION:Plural slice levels are respectively set to upper and lower waveforms, and the waveforms are simultaneously discriminated by plural pulse sampling circuits 51 to 55 and plural discriminator 71 to 75. A comparator circuit 200 judges in which slice level the number of errors is small by the results, and a slice level control circuit 100 controls to change more correct slice level value. Since the upper and lower slice levels are respectively and properly set to the asymmetry waveform in upper and lower parts, information reproducing can be executed correctly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for correctly reproducing a reproduced waveform in magnetic recording into information data, and more particularly to an MR device.
The present invention relates to a magnetic recording / reproducing apparatus capable of correctly reproducing even when the amplitude of a reproduced waveform is vertically asymmetrical such as when a head is used.

[0002]

2. Description of the Related Art In a conventional magnetic recording / reproducing apparatus, data is reproduced by a circuit as shown in FIG. The state of reproduction is shown in FIG. The role of the slice level and pulse extraction circuit in FIG. 1 is to remove an incorrect pulse in the 0 cross pulse made from the differential waveform. In particular,
The slice level is set to about half the 0-P value of the waveform amplitude, the waveform is cut according to the slice level to form a gate, and only the 0 cross pulse while the gate is open is extracted.

[0003]

However, according to the conventional technique, correct reproduction cannot be performed when the amplitude of the reproduced waveform is vertically asymmetrical as in the case of using the MR head as shown in FIG. This is because the slice level should originally be set to about half of the 0-P value of the waveform amplitude, whereas in the conventional technique, when the amplitude of the reproduced waveform is vertically asymmetrical, the slice level is set to the upper and lower (P, N). This is because it is impossible to set the slice level on the side) to a correct value for each. Therefore, in order to solve this problem, it is necessary to correctly set the slice level to about half the 0-P value of the upper and lower amplitudes.

[0004]

The means for solving the above-mentioned problems is to first set the upper and lower (P, N side) slice level values independently of each other. Secondly, the value of each slice level is made variable and controlled so that it becomes a correct value.

[0005]

As a result, the slice level can be set to a correct value even when the amplitude of the reproduced waveform is vertically asymmetrical as when using the MR head, and the information data can be reproduced correctly.

[0006]

EXAMPLE A first example is shown in FIGS. The principle will be described with reference to FIG. First, the slice level is set to a plurality of values above and below (meaning P, N, or positive or negative). At this time, it is assumed that the respective central values P and N are set to almost correct values. Next, the data obtained by discriminating the slice levels in the combinations shown in FIG. 5 are compared. At the time of comparison, the data discriminated by P / N is regarded as correct and the error is checked. For example, comparing + ΔV and −ΔV which is more correct at the level on the P side, P−ΔV has fewer errors. Therefore, it can be determined that the smaller level has the optimum value, and the level on the P side is controlled to be lowered. Similarly, the N side is controlled to be raised.

A circuit for realizing these is shown in FIG. Gates for each slice level are formed by the comparators 31-33 and 41-43, and the read pulse is extracted by the pulse extraction circuits 51-55 in the combination shown in FIG. The read pulse is discriminated simultaneously by the discriminators 71 to 75, the data is compared by the data comparison circuit 200, and the slice level control circuit 100 controls the slice level value according to the result to correct it. .. Here, the pulse extraction circuits 51 to 55 are the same as those shown in FIG.
In addition to a simple circuit using only ND and OR gates, a circuit that extracts the first 0 cross pulse after the gate is opened by a flip-flop can be configured by various methods.

Details of the data comparison circuit 200 are shown in FIG. First, E-OR circuits (exclusive OR devices) 201 and 2
By 04, the outputs of the discriminators 72 to 75 are exclusively ORed with the output of the discriminator 71. As a result, the error for the correct data discriminated at the slice level P / N can be found. This error is counted by the counters 206 to 209 within the time determined by the timer 205. By comparing the numerical values of these counters with the numerical comparators 210 and 211, it is judged which error is larger and whether the slice level should be raised or lowered.

Specifically, as shown in FIG. 7, the numerical comparator 2
In 10, when the value of the counter 206 is smaller than the value of the counter 207, a signal to increase the N level is output. Any method of outputting this signal may be used as long as it has an interface with the slice level control circuit 100. Here, in the numerical comparators 210 and 211, the judgment of the magnitude relation of the counter numerical values is as follows if the difference is within a certain fixed range:
It is more practical to judge that, and if it is more than that, judge as <or>. The value for the determination may be determined together with the timer time.

Details of the slice level control circuit 100 are shown in FIGS. In FIG. 8, the control circuit 101 receives a signal of an instruction to move the slice levels P and N up and down, converts the signal into a digital value, and the D / A converter 1
02 and the voltage P is obtained. + ΔV circuit 103 and −Δ
The V circuit 104 may use, for example, a diode. In FIG. 9, the control circuit 105 switches the switch 107 to change the voltage. At this time, the voltage to be supplied may be generated by, for example, the circuit 106 in which resistors are vertically connected.

The specific usage of the first embodiment described above is as follows. When the magnetic recording / reproducing apparatus is actually operated, that is, when the actual data is reproduced, the slice level control is always operated and adaptively controlled, and the test pattern is also used. It is possible to implement by various methods, such as a method of controlling only the above and fixing the slice level at the time of reproducing the actual data, or a method of performing a test at the time of shipping the device and setting (fixing) the optimum slice level. This test pattern can be recorded at a constant frequency or a random pattern. Further, in the first embodiment, since the initial setting values of the slice levels P and N need to be substantially correct values, it is necessary to set the initial values by making a judgment by looking at the reproduced waveform in advance or by using the method shown in the following embodiment. It needs to be adjusted.

Next, a second embodiment will be described with reference to FIG. First, input the reproduced waveform to the peak hold circuit 20,
Get the peak hold value. The peak hold value is averaged by the averaging circuit 21 and the slice level is set to approximately half the 0-P value of the waveform amplitude. If two sets of these circuits are used for each of P and N, the correct slice level can be set for each. In this embodiment, since the amplitude value of the waveform directly affects, it is desirable to operate with the reproduced waveform recorded and reproduced at a constant frequency. Therefore, instead of adaptively controlling, a method of controlling only the test pattern and fixing the slice level at the time of reproducing the actual data, or performing a test at the time of shipping the device and setting (fixing) the optimum slice level Method is preferred.

Next, a third embodiment will be described with reference to FIG. First, the reproduced waveform is input to the integrating circuit 22 to obtain an integrated value. This integrated value is input to the averaging circuit 21. After that, the slice level is set as in the second embodiment. If two sets of these circuits are used for each of P and N, the correct slice level can be set. Since the amplitude value of the waveform directly affects the present embodiment as in the second embodiment, a method of controlling only the test pattern and fixing the slice level when reproducing the actual data, or performing a test at the time of shipment of the device to perform the optimum slice It is desirable to set (fix) the level.

[0014]

According to the present invention, it is possible to correctly reproduce information data even when the amplitude of a reproduced waveform is vertically asymmetrical as when an MR head is used.

[Brief description of drawings]

FIG. 1 is a reproducing circuit diagram in a conventional magnetic recording / reproducing apparatus.

FIG. 2 is an explanatory diagram showing a reproduction principle in a conventional technique.

FIG. 3 is an explanatory diagram showing a defect in the conventional technique.

FIG. 4 is a block diagram showing an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the principle of controlling the slice level.

FIG. 6 is a block diagram showing a data comparison circuit of the present invention.

FIG. 7 is an explanatory diagram showing the operation of the data comparison circuit of the present invention.

FIG. 8 is a slice level control circuit diagram of the present invention.

FIG. 9 is a slice level control circuit diagram of the present invention.

FIG. 10 is a waveform diagram (a) and a block diagram (b) showing another embodiment of the present invention.

FIG. 11 is a waveform diagram (a) and a block diagram (b) showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Differentiation circuit, 2 ... 0 cross pulse generation circuit, 31, 3
2, 33, 41, 42, 43 ... Comparators, 51, 52, 5
3, 54, 55 ... Pulse extraction circuit, 6 ... PLL, 71,
72, 73, 74, 75 ... Discriminator, 100 ... Slice level control circuit, 200 ... Data comparison circuit.

Claims (11)

[Claims] 1. In a device for reproducing a magnetically recorded signal, a plurality of slice levels for generating gates corresponding to the positive side and the negative side of a reproduced waveform, and the value of the slice level are used as the reproduced waveform amplitude. A magnetic recording / reproducing apparatus provided with a control circuit for controlling according to the size. 2. A plurality of read pulse extraction circuits for extracting a read pulse from one of the plurality of slice levels on the positive side and one on the negative side respectively, and the read pulses are discriminated at the same time. A magnetic recording / reproducing apparatus including a plurality of discriminators, a data comparison circuit that compares discrimination data, and a slice level control circuit that controls a slice level according to a comparison result of the data. 3. The circuit according to claim 2, wherein a circuit for comparing the discrimination data to check for the presence of an error, a counter for counting the number of errors, a comparator for comparing the numerical values of the counter, and counting errors for a certain period of time. And a magnetic recording / reproducing apparatus including a timer for performing the operation. 4. A magnetic recording / reproducing apparatus having a D / A converter according to claim 2 or 3. 5. A magnetic recording / reproducing apparatus according to claim 2, further comprising a plurality of voltage sources and a switch for switching the plurality of voltages. 6. An apparatus for reproducing a magnetically recorded signal, a peak hold circuit for obtaining peak values on the positive side and negative side of a reproduced waveform, a circuit for averaging the peak hold values, and the average value. And a circuit for setting a slice level according to the magnetic recording / reproducing apparatus. 7. A device for reproducing a magnetically recorded signal, a circuit for integrating the positive and negative waveforms of a reproduced waveform, a circuit for averaging the integrated values, and a slice level according to the average value. And a circuit for setting the magnetic recording / reproducing apparatus. 8. The method according to claim 1, 2, 3, 4 or 5.
A magnetic recording / reproducing apparatus in which the initial value of the slice level is determined by the circuit according to claim 6. 9. The method according to claim 1, 2, 3, 4, or 5,
The magnetic recording / reproducing apparatus which determines the initial value of the slice level by the circuit according to claim 7. 10. Claims 1, 2, 3, 4, 5, 6, 7, 8
Alternatively, in 9, the magnetic recording / reproducing apparatus which controls the slice level at the time of reproducing the actual data and adaptively controls the slice level. 11. Claims 1, 2, 3, 4, 5, 6, 7, 8
In the magnetic recording / reproducing apparatus, the slice level is set to a fixed value after being controlled by a predetermined test pattern, and the slice level is not controlled during actual data reproduction.