JPS6394411A - Reading signal reproducing circuit for disk storage device - Google Patents

Abstract

PURPOSE:To widely decrease the probability of an error generation by changing a threshold, which comes to be a foundation on the action of a positive negative discriminating circuit generated by a threshold generating circuit, in accordance with the diameter direction position of a head on a disk. CONSTITUTION:A reading signal AS from an amplifier circuit 2 is in this case, composed of two differential signals and an output is sent to a peak detecting circuit 10 and a positive negative discriminating circuit 20. Here, the circuit 10 outputs a timing pulse TP to show the peak position of the reading signal AS. The circuit 20 compares respectively the positive negative waveform held by the reading signal with a threshold and outputs a signal to display the positive and negative condition of the analog waveform of the reading signal. A threshold generating circuit 30 to give a threshold Th to the circuit 20 receives a diameter direction position signal SP and generates the threshold in accordance with the diameter direction position of a head. The output of the circuit 20 is referred to, a timing pulse selecting circuit 40 selects the timing pulse out of the signal TP from the circuit 10 and outputs it as a reproducing signal RS.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a transducer for transducing the recorded contents of information written in a predetermined magnetic pattern in which N and S $1 areas alternate on a disk of a disk storage device such as a fixed disk device. The present invention relates to a circuit for reproducing a pulse-like signal indicating the boundary between the N and 3 regions from an analog waveform read signal read through a head.

[Prior art and its problems]

As is well known, information written on a disk of a disk storage device is basically a magnetic pattern in which N poles and sB sequentially alternate, and the N pole along the longitudinal direction of the track is
The width of the 611 area and the 395 area is a predetermined formant, for example, MFM (Modified Frequency).
-cy Modulation). This area width has a meaning corresponding to the data of 0 and 1 which is the recorded information, and the head that reads this is a kind of magnetic sensor, but usually the magnetic flux from the N and 3 areas moving underneath it. Since the electromotive force accompanying the change in is output as a read signal, the position of the boundary between the N and S regions, which is the source of the magnetic flux change, is detected. On the other hand, as long as the position of this boundary can be detected accurately, the area between the two subsequent boundaries is the width of the area mentioned above, so it is relatively easy to reproduce the original data recorded on the disk. can do. However, as you can easily imagine, the read signal output from the head has an analog waveform with considerable distortion and noise, and it is impossible to directly reproduce the original data from this read signal. A so-called signal reproducing circuit is provided in the area to process the read signal and convert it into a digital signal indicating the boundary between the N and 3 areas. This is the read signal reproducing circuit that is the subject of the present invention, and a conventional example thereof will be briefly explained below with reference to the drawings. Figure 5 shows an outline of the circuit configuration.The weak read signal AS from the head of the disk storage device is amplified by a two-man powered, two-output amplifier circuit 2 with an AGC, as shown in Figure 6). Has an analog waveform. The corresponding magnetic pattern on the track T is shown in fal in the figure, and as can be seen from the figure, the read signal As has positive and negative peak values at the boundary between the N and S regions. The peak detection circuit 3 is for detecting this peak position.As is well known, for example, the read signal is differentiated, the peak position is determined from the zero cross point of the differentiated waveform, and the output is as shown in FIG. 7 +dl. A short timing pulse TP is generated. Therefore, this timing pulse TP could be used as a reproduced signal as it is, but since the analog waveform of the read signal AS often has a shoulder sh as shown in the figure,
There is a risk that this shoulder sh will be mistakenly recognized as a peak and erroneous timing pulses TPI, TP2, etc. will be generated. The comparator 4 is for removing this erroneous signal, and compares the read signal AsO differential output from the amplifier circuit 2 with each other to determine whether the analog waveform is positive or negative.
A state signal SS is emitted. In this example, the open state signal SS, with which the read signal ^S has a positive waveform, takes the value "1" and during the negative waveform it takes the value "0". D type flip flop 5
is for synthesizing the timing pulse TP and the state signal SS, and receives the latter at its D input and the former at its clock C, so even if an erroneous timing pulse ↑P1 occurs, the current input to the D input is When the status signal SS is rlJ and has been sent with the previous timing pulse,
The cent state of flip-flop 5 is the timing pulse T.
It remains unchanged even when receiving PI, and the timing pulse TPI
The composite signal CS is output from the Q output of the flip-flop 5 as shown at +81 in FIG. As shown in the figure, the erroneous timing pulse TPI, which is converted into a pulsed reproduction signal R3, is thinned out from this reproduction signal R3. However, the switching operation of the status signal SS of the comparator 4 tends to become unstable near the shoulder sh of the read signal As, and the status signal SS may be switched before an erroneous timing pulse is generated. TP2
This is the case when, immediately before its occurrence, the state signal SS
has been switched from rOJ to "1". Therefore, the composite signal C3 that should originally be sent at the next timing pulse is III k? in the figure. As shown by i, it is set prematurely, and an incorrect reproduction signal R32 is output accordingly. As a countermeasure against this, a threshold value is set for the operation of the comparator 4,
Examples are shown in FIGS. 7 and 8. FIG. 7 is an example in which the operation of the comparator 4 in FIG.
Positive and negative threshold values Thp4hn are set as shown in FIG. Therefore, the state signal SS from comparator 4, shown in (7) in the same figure, is switched when the read signal ^S crosses the positive threshold and then when it crosses the negative threshold. The first time it is switched again. The positive and negative threshold widths, that is, the operational hysteresis widths are set so that the thresholds do not cut the shoulder of the read signal ^S, so the status signal S
The switching operation of S becomes reliable, and as shown in fc) in the same figure, the timing pulse TP is replaced by an incorrect timing pulse T.
Even if PI and TP2 are included, the composite signal C8 of them and the status signal SS is not disturbed by it and switches normally, and the reproduced signal R3 is correctly generated from it as shown in el of the same figure. FIG. 8 shows read signals AS1. Focusing on the fact that AS2 can be used, two comparators 4 shown in Fig. 2 are provided to compare each of both read signals with a common threshold Th.As can be easily understood, the function is as follows: This is the same as the case in FIG. However, in this case, different state signals SS1. SS2 is the same figure (bl, (
As shown in Figure 0, the state signal 5S can be easily combined into one state signal SS shown in +d+ in the figure.
The state signal SS of Fig. 6+81 can be set so that the state signal SS rises when the IO side rises and falls when the state signal SS2 falls.
is homologous to the previous B signal SS shown in FIG. 7, 1dl, and has the same function of erasing erroneous timing pulses. With the conventional technology explained above, even if the analog waveform of the read signal has a deformation like the shoulder described above, it should be possible to skillfully eliminate the erroneous timing pulses that may occur due to the deformation and obtain a correct reproduced signal. However, in reality, it is not always perfect, and in the prior art described above, irregularities may still occur in the reproduced signal, causing errors in data reading. The reason for this is thought to be that the deformation of the read signal is not only simple such as a shoulder, but also that unpredictable deformation occurs in the analog waveform of the read signal. However, since the probability of occurrence of an incorrectly reproduced signal or a read error based on it is essentially low, it has been difficult to find out how the read signal is deformed to cause an error and take countermeasures.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to improve conventional playback circuits so that the risk of read errors in a disk storage device is further reduced even if the read signal is significantly distorted.

[Key points of the invention]

The present invention has succeeded in reducing the error rate of the reproduced signal by focusing on the fact that the deformation of the read signal that causes the erroneous reproduced signal is dependent on the position of the head in the inner radial direction of the disk. According to the above, the above-mentioned purpose is to provide a read signal reproducing circuit of a disk storage device with a peak detection circuit that detects a candidate peak position of an analog waveform from a read signal and emits a timing pulse indicating the candidate position, and a peak detection circuit that detects a candidate peak position of an analog waveform from a read signal and generates a timing pulse indicating the candidate position. A positive/negative discrimination circuit that compares each waveform with a threshold value and generates a status signal representing the positive/negative status of the analog waveform of the read signal, and a positive/negative discrimination circuit that generates a threshold value depending on the radial position of the head within the disk. A threshold generation circuit provides a positive/negative discrimination circuit with a timing pulse from the peak detection circuit and a status signal from the positive/negative discrimination circuit, and determines the positive/negative state of the analog waveform of the read signal indicated by the status signal from within the timing pulse. This is achieved by comprising a timing pulse selection circuit that selects a suitable timing pulse and issues it as a reproduction signal of the read signal. The dependence of the above-described deformation of the read signal on the radial position will be explained with reference to FIG. Writing information to the trunk T of a disk storage device is performed using either N or S in any of the known methods.
The width of each area is a mixture of wide widths as shown in Figure 9 fa+ and narrow widths as shown in Figure 9 (bl).The electromotive force generated in the head is originally caused by the boundary between the N and S areas. However, due to the influence of the inductance of the head, this electromotive force has a peak shape, but it has a slight base in the longitudinal direction of the trunk, that is, the time axis, and when the head moves from the S tJ region to the N region or The polarity has a positive or negative value depending on whether it is the opposite or not. In Fig. 9, such positive and negative electromotive forces based on one boundary are shown by chain lines Vp and Vn.The read signal As from the head is, of course, a composite of these electromotive forces Vp and Vn over time, and the above-mentioned shoulder sh is likely to occur in the wide area shown in fal in the same figure, as shown in the figure. Such a shoulder will not occur where the width of the region is narrow, but the peak value of one of the positive and negative electromotive forces Vp and Vn will be more likely to be canceled out by the base of the other, and the peak value PV will be lower than where the width of the region is wide. It is easy to see that this decrease in the peak value of the read signal is due to the fact that the recording density of information on the track is increased and the area width is close to 1n as in recent high-density recording. In addition, since the amount of information recorded on one track is the same whether the track is on the outer or inner side of the disk, the area width on the outer side Shoulders tend to occur in the read signal where the width of the read signal is wide, and the peak value of the read signal decreases significantly especially where the area width is narrow on the inner diameter side.As a result of various experiments and analyses, the inventor of the present invention When the threshold value to be applied to the positive/negative discrimination circuit in the above configuration is selected to avoid errors caused by the shoulders of the It was found that the probability of read errors tends to increase.The cause of this is presumed to be the decrease in the peak value of the read signal mentioned above, and the threshold value for the positive/negative discrimination circuit is reduced for the inner trunk. In this case, as shown in Figure 5 above, since an amplifier circuit with AGC is provided for the read signal, even if the peak value of the read signal from the inner diameter trunk decreases, It is conceivable that this could be corrected automatically, but the track on the inner diameter side also has wide areas and narrow areas, and the peak value of the read signal from the wide area does not decrease much. The high peak value acts on the average value of the high and low peaks, and cannot sufficiently raise the level of the read signal with the low peak value sandwiched between the high peak values.Therefore, the threshold value for the inner trunk It is thought that lowering the value is effective in preventing errors. On the other hand, it was found that setting this threshold value higher than conventionally considered appropriate for the outer diameter side would further reduce the probability of errors. The reason for this is not necessarily clear, but the position where the shoulder occurs does not necessarily occur at the zero-crossing point of the read signal, and may fluctuate slightly above and below it for some reason. This is considered to be because it is advantageous to make the threshold value somewhat higher. Therefore, in the present invention, a threshold generation circuit is provided that generates a threshold depending on the position of the head in the inner diameter direction of the disk, thereby making it possible to control the operation of the positive/negative discrimination circuit. As can be seen from the above findings, it is particularly advantageous to reduce the cough threshold as the position of the head inside the disk goes from the outer trunk to the inner trunk in order to prevent errors. Other advantageous embodiments for carrying out the invention are as described in the next section.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The figure shows a read signal reproducing circuit for a disk storage device according to the invention together with a head 1 and an amplifier circuit 2 for a read signal As from the head. In this example, the read signal AS from the amplifier circuit 2 consists of two differential signals, including a peak detection circuit 10 and a positive/negative discrimination circuit 20.
given to. The peak detection circuit 10 is the same as the conventional example (
For example, it is composed of a differentiating circuit and a zero-crossing point detection circuit, and emits a timing pulse TP that indicates the zero-crossing point of the differential signal, that is, the peak position of the read signal.
In addition to timing pulses that are suitable for output as a signal, it also includes erroneous timing pulses associated with the shoulders of the read signal, and in this sense, it is only a candidate for the reproduced signal R3 that should indicate the peak position on the analog waveform of the read signal. This is the timing pulse. In the illustrated example, the positive/negative discrimination circuit 20 includes two comparators 2.
1 and 22 and one D type flip-flop 23, each of the comparators 21 and 22 receives two differential signals of the read signal ASI and AS2 at one input thereof, respectively.
, and the other input receives a signal indicating a common threshold Th in this example. Therefore, the operations of these comparators 21 and 22 are similar to those shown previously in FIG.
A status signal SSI, 352, designated bl, IcI is issued. Flip-flop 23 receives both these status signals SS1.
It is for the synthesis of SS2, receives the state signal SSI at its D input and clear input, and receives the state signal SS2 at the clock input C.
Therefore, it is set at the rising edge of the status signal SS1 and reset at the falling edge of the status signal SS2.
A synthesized state signal SS shown in the figure (dl) is generated from its Q output.The threshold generation circuit 30 that provides the threshold value Th, which is the operating reference for the positive/negative discrimination circuit 20, is arranged in the radial direction in this example. In response to the position signal PS, the threshold value according to the radial position of the head is switched discontinuously or stepwise.As is well known, a disk storage device usually includes a device for controlling its operation. A microprocessor is incorporated in which, for radial operation of the head, the current position of the head is stored, usually in the form of a track number starting from the outer diameter. In addition to the head position, there are other things that need to be controlled, such as the magnitude of the current for writing information to the disk and the gain of the so-called servo information amplifier circuit, both of which cause switching signals to be generated depending on the radial position of the head. Therefore, the radial position signal PS used in the implementation of the present invention can usually be made by using these switching signals themselves, and in this example, two radial position signals Psi and PS which are issued sequentially are used.
2, the threshold value Th is switched in three stages according to the radial position. The threshold value generating circuit 30 of the illustrated example is powered from a constant voltage source or a constant current source, and is connected to common resistors 31 and 3.
This is a setting circuit for a threshold value Th determined by the ratio of the combined resistance of the individual resistors 32, 33, and 34, and the radial position signal Psi is sequentially applied as the head moves from the outer diameter side to the inner diameter side of the disk. By sequentially turning on the transistors 33 and 35 using PS2, the above-mentioned combined resistance and therefore the output threshold value are lowered stepwise. It is usually sufficient for the operation of the threshold generation circuit 30 to change the threshold value stepwise in this way, but if it is desired to change the threshold value continuously, for example, the current state of the head recorded in the aforementioned processor may be A bias value related to the trunk number value is created from the track number of the track number via a DA converter, and a signal obtained by subtracting this variable bias value from a fixed threshold value is output as a threshold value to the positive/negative discrimination circuit 20. be able to. The timing pulse selection circuit 40 selects a timing pulse that truly indicates the peak position of the analog waveform of the read signal from among the timing pulses TP from the peak detection circuit 10 while referring to the status signal SS from the positive/negative discrimination circuit 20. It is for outputting as a reproduced signal RS, and in the illustrated example, it consists of a D-type flip-flop 41 and a bidirectional one-shot circuit 42, of which the former plays the role of selecting a timing pulse. Since the state signal SS is given to the D input of the flip-flop 41 and the timing pulse TP is given to the clock C,
The flip-flop 41 is edge-triggered to perform a cent or recent operation only by the first timing pulse TP that arrives at its C input after the state signal to its D input toggles, and subsequently by the timing pulse TP under the same state signal SSO. This behavior is the same as that shown in Figure 7 (bl~+dl), and the shoulder sh in the analog waveform of the read signal ^S
Incorrect timing pulse TPI, TP2 due to etc.
A composite signal CS is created by ignoring Therefore, the rise and fall of this composite signal C3 indicate the correct peak position in the analog waveform of the read signal,
Although it may be used as a reproduced signal as it is, normally it is converted into a timing pulse train indicating the peak position via the one-shot circuit 42 in order to be compatible with the above-mentioned MFM system, etc., and then output as the reproduced signal R3. As is well known, this MFM reproduction signal is converted into an NRZ signal and then converted into parallel digital data by a serial/parallel conversion circuit. FIG. 2 shows a different embodiment of the invention, previously shown in FIG.
Corresponding to the one using the comparator with hysteresis shown in Figure (al), only the positive/negative discrimination circuit 20 and the threshold generation circuit 30 are shown in the figure.The core of the positive/negative discrimination circuit 20 in this example is calculation. An amplifier 24 is supplied with only one analog waveform of the read signal As.The two outputs of the operational amplifier 24 are kept in potential balance by a pair of resistors 24a and 24b, and the interconnection of both resistors The potential at the point is kept stable by a potential setting circuit 25 consisting of two other resistors 25a, 25b and a capacitor 25c.The capacitor 25c is for stabilizing the potential by absorbing fluctuations in the power supply voltage. The feedback circuit for creating operational hysteresis is the threshold generation circuit 30 itself, and includes a fixed resistor 37, a resistor 38 for adjusting the hysteresis width, and an electronic switch 39 for inserting and removing the cough resistor 38. The radial position signal in this example is represented by a single signal ps, and when the electronic switch 39 is turned on by this, the combined resistance value of both resistors 37 and 38 decreases, and the ratio between this and resistor 24b decreases. The positive/negative discrimination circuit 20 in which the operational hysterine width is set or adjusted in this way is shown in FIG.
As shown in +, two positive and negative thresholds Thp, Thn
It operates as a comparator with a comparison result signal and outputs the above-mentioned state a signal SS. Now that we have finished explaining the circuit configuration and its basic operation, we will finally explain the read error prevention operation of the circuit of the present invention in comparison with the case of the prior art with reference to FIGS. 3 and 4. FIG. 3 shows a case where the head position is on the inner diameter side, the area width of the magnetic pattern written on the disk is narrow, and the peak value of the read signal As is low as described above. As shown in ta+ in the figure, the threshold value for the inner diameter side in this case is the threshold value Th for the outer diameter side shown by the chain line.
. According to the present invention, the value Ti1l is set to a sufficiently small value so as to intersect with the low peak value of the read signal AS.
It is possible to reliably generate the state signal SS shown in FIG. For the threshold,
Since the threshold value ThO for the inner diameter side is the same as the threshold value ThO for the outer diameter side, it cannot intersect with the analog waveform of the read signal. Since the signal SS is not generated and therefore the composite signal shown in the figure (fl) is not generated, the reproduced signal is lost. In Figure 4, the head is on the outer diameter side and the area width of the magnetic pattern is small. This shows a case where the shoulder sh of the read signal AS is wide and slightly shifted upward in the figure, and the analog waveform of that part of the read signal is enlarged in FIG. 181. In this case According to the present invention, the threshold value Tho of is set higher than the threshold value Thl for the inner diameter side shown by the chain line in the figure.
Since the state signal SS of bl rises at the intersection with the read signal above the shoulder sh, the erroneous timing pulse ↑P shown in the same figure (C), which tends to occur near the previous shoulder.
1, the operation of the timing pulse selection circuit 40 is not disturbed, and the composite signal CS is raised only by the correct timing pulse TP as shown in +d) in the figure. The threshold Th in this case as in the prior art. is the same as the threshold value Thi for the inner diameter side, the status signal SS from the positive/negative discrimination circuit 20 tends to rise at the beginning of the shoulder sh as shown at +61 in the figure, and the timing pulse selection circuit 4o Annoyed by the wrong timing pulse TPI, the composite signal CS rises at an incorrect time as shown in FIG. 2(e). In addition to the embodiments described above, the present invention can be implemented in various ways within the scope of the invention.For example, in the embodiment shown in FIG. Although the values are given from the positive/negative discrimination circuit, depending on the nature of the analog waveform of the read signal, it is often advantageous in terms of design or operation to be able to adjust these thresholds independently.

【Effect of the invention】

As explained above, in the present invention, the threshold value generated by the threshold generation circuit, which is the basis of the operation of the positive/negative discrimination circuit, can be changed according to the radial position of the head on the disk. , the threshold value can be selected to best suit the deformation of the analog waveform indicated by the read signal from the head, which could not be countered by conventional technology, and this allows the timing pulse selection circuit to Since the correct reproduced signal is generated without being influenced by incorrect timing pulses from the peak detection circuit, although reading errors cannot be completely eliminated, the probability of error occurrence is significantly reduced compared to the conventional technology. Can be done. That is, the read signal from the wide area portion of the recorded magnetic pattern on the outer track of the disk has a shoulder on its analog waveform that is mistaken for a zero cross point, or the level of the MR portion is positive or negative. Even if there is a slight deviation in the negative direction, by raising the threshold that the threshold generation circuit generates for the outer diameter side continuation signal, the intersection point of the read signal with the analog waveform is uniquely determined. This allows the positive/negative discrimination circuit to switch the signal No. 118 at the correct time. Furthermore, even if the peak value of the read signal from the narrow area of the magnetic pattern on the inner track of the disk becomes too small, the threshold value for the inner read signal can be lowered. By making sure that the peak part of the analog waveform of the read signal intersects with the peak part of the analog waveform of the read signal, the positive/negative discrimination circuit can switch the state signal more reliably. If the status signal from the positive/negative discrimination circuit is switched reliably and at the correct time in this way,
The timing pulse selection circuit ensures that erroneous timing pulses that may be included in the timing pulses from the peak detection circuit are not ignored or removed, and a correct reproduction signal can be output from the read signal reproduction circuit. As described above, the circuit of the present invention can improve the reliability of the read operation of the disk storage device by making the operation of the reproducing circuit more accurate than that of the prior art.

[Brief explanation of the drawing]

1 to 4 are for explanation of the present invention, and the inner cylinder 1
1 is a circuit diagram showing a first embodiment of a read signal reproducing circuit for a disk storage device according to the present invention together with related circuits; FIG. 2 is a circuit diagram showing main parts of a second embodiment of the present invention; FIGS. FIG. 4 is a waveform chart for main signals in the reproducing circuit, showing the operation of the circuit of the present invention in comparison with the operation in the prior art when the head is located on the inner diameter side and the outer diameter side of the disk, respectively. 5 and 6 are for explanation of the prior art; hand-drawn figure 5 is a block circuit diagram showing the general configuration of a conventional read signal reproducing circuit, and figure 6 is a waveform diagram of main signals in the circuit. . 7 and 8 are waveform diagrams of main signals in the conventional circuit and the circuit of the present invention, and FIG. 9 is a waveform diagram of the read signal illustrating how the analog waveform of the read signal is deformed. 1: head, amplifier circuit with 2nAGC, lO: peak detection circuit, 20: positive/negative discrimination circuit, 21.22: comparator, 23: flip-flop, 24: operational amplifier, 30
Rainbow threshold generation circuit, 31-34 Rainbow threshold setting resistor, 35.36iL threshold switching transistor, 33.3
8: Hysteresis width setting resistor, 39 Electronic threshold switching switch, 40: Timing pulse selection circuit, 41
: flip-flop, 42: one-shit circuit, AS:
Read signal, ASl, AS2: Differential output of read signal, C8
: Composite signal of timing pulse and status signal, PS, P
Sl, PS2: Radial position signal, Pv: Peak value of read signal, R5: Reproduction signal, R52: Erroneous reproduction signal, s
h: Shoulder in analog waveform of m-take signal, SS, S51° SS2: Status signal, Tj) rank, ThjL threshold, T
hp. Thn: positive and negative threshold, TP: timing pulse, T
P.I. TP2: erroneous timing pulse, Vp, Vn: positive and negative electromotive force within the belly button. , -'5 11 countries 5c Figure 2 Figure 3 Figure 4 Figure 5 Fight S2 Figure 6

Claims (1)

[Scope of Claims] 1) Recorded content of information written in a predetermined magnetic pattern in which both N and S areas alternate on a disk of a disk storage device is read from an analog waveform read signal read out via a transducer head. , a peak detection circuit which is a circuit for reproducing a pulse-like signal indicating the boundary between the two regions, and which detects a peak position candidate of the analog waveform from the read signal and emits a timing pulse indicating the candidate position;
A positive/negative discrimination circuit that compares the positive and negative waveforms of the read signal with threshold values and generates a status signal representing the positive/negative status of the analog waveform of the read signal, and a threshold value that corresponds to the radial position of the head within the disk. A threshold generation circuit generates a threshold value and supplies it to the positive/negative discrimination circuit, receives a timing pulse from the peak detection circuit and a status signal from the positive/negative discrimination circuit, and generates an analog waveform of the read signal indicated by the status signal from the timing pulse. A read signal reproducing circuit for a disk storage device, comprising: a timing pulse selection circuit that selects a timing pulse that matches the positive/negative state of the read signal and issues it as a read signal reproduction signal. 2) The circuit according to claim 1, characterized in that the threshold generation circuit decreases the threshold value as the position of the head inside the disk goes from the outer diameter side to the inner diameter side. A read signal reproducing circuit for a disk storage device. 3) The circuit according to claim 1 or 2, characterized in that the threshold value generated from the threshold generation circuit is discontinuously switched depending on the radial position of the head within the disk. A read signal reproducing circuit for a disk storage device. 4) Read signal reproduction of a disk storage device in the circuit according to claim 1, characterized in that the threshold generation circuit generates a single threshold value for positive and negative analog waveforms of the read signal. circuit. 5) In the circuit according to claim 4, each of the positive/negative discrimination circuits receives a single threshold value in common at one input, and a positive analog waveform and a negative analog waveform of the read signal at the other input. includes two comparison circuits each receiving
1. A read signal reproducing circuit for a disk storage device, characterized in that a positive/negative state of an analog waveform of a read signal indicated by a status signal is switched according to comparison outputs of both comparison circuits. 6) In the circuit according to claim 4, the positive/negative discrimination circuit includes one comparison circuit that performs a hysteresis operation, and the hysteresis width of the operation is specified by a threshold value from a threshold generation circuit. A read signal reproducing circuit for a disk storage device, characterized in that: 7) A read signal reproducing circuit for a disk storage device, characterized in that, in the circuit according to claim 1, the positive/negative discrimination circuit emits a single status signal.