JPH0869606A - Slice level setting device and magnetic recorder using the same - Google Patents

Abstract

PURPOSE: To prevent the erroneous detection of information by varying a slice level for signal detection even if the waveform peaks of reproduced waveforms fall below the slice level for detecting the signals by the influence of an undershoot. CONSTITUTION: The isolated wave signals recorded on a recording medium 1 are read out and the time Tf from the front undershoot (part of S1) of the waveforms of these signals to the peak points P and the time Tr from the peak points P to the rear undershoot (part of S2) are respectively counted by a reference clock in an undershoot counting means 11. The presence or absence and polarity of the peaks in the front position of the time Tf and the rear position of the time Tr from the respective peak points P in the read out reproducing waveforms are discriminated and the undershoot detection signal is outputted by an undershoot position detecting means 12 at the time of reproducing the data from the recording medium 1. A slice level setter 14 for setting the slice level of the pulse detection at a low level when the detection signal is received is disposed to prevent the erroneous detection of the information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detection method using a variable slice level and a magnetic recording apparatus using the same.

As a signal detection method in a magnetic recording device used for an information processing device, a method of reproducing a digital signal by detecting a peak level of a read signal waveform by a predetermined slice level is used.

[0003]

2. Description of the Related Art Conventionally, in a magnetic recording apparatus, when a peak level of a read signal waveform is detected by a slice level, detection is performed at a preset fixed slice level even when there is a change in a data pattern. Was.

However, when detecting the peak level of the read / reproduced waveform based on the slice level, if the peak of the read signal waveform falls below the slice level due to the effect of undershoot, the peak detection of the read signal waveform is appropriately performed. In some cases, the reproduction cannot be performed, and as a result, there is a problem that a reproduction error occurs.

On the other hand, in Japanese Patent Application Laid-Open No. 56-54120, when a read signal is rectified and smoothed to generate a slice level, the charge time constant of the smoothing circuit is reduced and the discharge time constant is increased. By performing amplitude discrimination with a slight peak hold, even if a sudden signal drop due to medium modulation or the like occurs, the discharge time constant of the smoothing circuit is reduced only in that portion to improve the followability of the slice level. It is described that normal amplitude discrimination can be performed.

In Japanese Patent Application Laid-Open No. 63-193377, a slice level for detecting the amplitude of an analog waveform is determined by setting an amplitude hold voltage from an amplitude hold circuit to which a peak detection signal detecting a peak of the analog waveform is input. It is described that, even when the amplitude of the analog waveform fluctuates, the slice level also fluctuates in accordance with the amplitude, thereby preventing loss of the amplitude detection signal.

Further, in Japanese Patent Application Laid-Open No. 2-81368, a peak value of a read data analog signal is held by a peak hold circuit, A / D converted, and sent to a processor. A slice level is calculated, and this is D / A converted to generate a slice voltage. It is described that the processor shifts the slice level to + or-in accordance with the degree of occurrence of a data reproduction error due to the slice level so that good signal reproduction can always be performed.

[0008]

When detecting the peak level of the read / reproduced waveform at the slice level, if the peak of the read signal waveform falls below the slice level due to the undershoot, depending on the fixed slice level. There is a problem that the peak detection of the read signal waveform cannot be properly performed, resulting in a reproduction error.

On the other hand, in each of the above prior arts, the peak level of the read signal waveform can be appropriately detected by changing the slice level in accordance with the change in the amplitude of the input analog signal. In addition, there is a problem that an effective operation cannot be performed with respect to a drop in the peak level of a signal waveform caused by the influence of undershoot.

[0010]

An object of the present invention is to provide a slice level setting device capable of appropriately detecting a peak of a read signal waveform even when a peak drop due to the influence of undershoot occurs, and a magnetic recording device using the same. That is its purpose.

[0011]

Therefore, in the present invention, a solitary wave signal recorded on a recording medium is read out, and a time Tf from the forward undershoot to the peak point of the isolated signal waveform and a time Tf from the peak point to the rear side. Undershoot counting means for counting the time Tr until the undershoot by a reference clock, and a position in front of the time Tf and behind the time Tr from each peak point in the reproduced waveform read out when the data is reproduced from the recording medium. And an undershoot position detecting means for outputting an undershoot detection signal by discriminating presence / absence and a polarity of a peak, and a slice level control means for setting a low slice level for pulse detection when the undershoot detection signal is received. , Is adopted.

Further, the slice level control means operates at time T.
f A first slice level setting function for setting a slice level when receiving a first undershoot detection signal indicating that both the front and the rear of the time Tr have been detected, and only one of the front of the time Tf and the rear of the time Tr. A second slice level setting function for setting a slice level when a second undershoot detection signal indicating that detection has been received may be provided.

Further, the undershoot position detecting means counts the time Tf from the undershoot to the peak point of the isolated signal waveform and the time Tr from the peak point to the back undershoot of the isolated signal waveform by the reference clock for each track of the recording medium. A track-by-track undershoot counting function may be provided.

According to the present invention, there are provided a slice level setting device, a magnetic disk medium, a head for reproducing data recorded on the magnetic disk, an amplifier for amplifying a reproduced signal reproduced by the head, and A low-pass filter for waveform-compensating the amplified reproduced signal; a delay unit for delaying the reproduced signal output from the low-pass filter for a certain period of time; and a pulse signal at a slice level set by a slice level setting device for the reproduced signal in the delay unit. A signal detector that converts the signal into a signal, a data discriminator that decodes the pulse signal output by the signal detector, and an interface circuit that controls data transfer of the data output by the data discriminator to a higher-level device. Is adopted.

The present invention aims to achieve the above-mentioned object by these means.

[0016]

According to the first aspect of the present invention, the undershoot counting means reads out the solitary wave signal recorded on the recording medium, and calculates the time Tf from the forward undershoot to the peak point of the solitary signal waveform and the peak Tp. The time Tr from the point to the rear undershoot is counted in advance by the reference clock. The undershoot position detecting means, when actually reproducing data from the recording medium, determines the presence or absence and the polarity of the peak at a position before the time Tf and after the time Tr from each peak point in the read reproduced waveform. And outputs an undershoot detection signal. Then, the slice level control means sets the slice detection pulse level low when the undershoot detection signal is received. Therefore, even if the level drops due to the undershoot, the slice level is set according to the drop.

According to the second aspect of the present invention, the slice level control means sets the slice detection pulse level when the first undershoot detection signal indicating that both the time Tf forward and the time Tr backward are detected is received. Set to the first slice level. Further, when a second undershoot detection signal indicating that only one of the front of the time Tf and the rear of the time Tr is detected is received, the slice level is set to the second slice level. The slice level when the undershoot detection signal is not received is the maximum, the next is the second slice level, and the first slice level is the lowest. Therefore, a plurality of preset slice levels are selected and set according to the type of the undershoot detection signal.

According to the third aspect of the present invention, the undershoot position detecting means includes the time Tf from the undershoot to the peak point of the isolated signal waveform and the time Tr from the peak point to the rear undershoot for each track of the recording medium. And are each counted by the reference clock. In response to this, the undershoot position detecting means refers to the track position of the read reproduction waveform when actually reproducing the data from the recording medium, and refers to the position ahead of time Tf and behind time Tr from each peak point. The presence / absence of a peak and the polarity are discriminated. Therefore, the position of the undershoot is accurately detected even when the period of the isolated signal waveform is different between the inner circumference side and the outer circumference side of the track.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a slice level setting device according to the present invention. The slice level setting device reads a solitary wave signal recorded on a disk 1 as a recording medium, and a time Tf from a front undershoot to a peak point of the solitary signal waveform and a time from the peak point to a rear undershoot. And an undershoot counting means 11 for counting Tr by a reference clock, and a time Tf from each peak point in the read reproduced waveform when reproducing data from the recording medium.
Undershoot position detecting means 12 for judging the presence or absence and polarity of a peak at a position before and after the time Tr and outputting an undershoot detection signal, and setting a low slice level for pulse detection when the undershoot detection signal is received. And a slice level control unit 13.

This will be described in detail. FIG. 2 is a waveform diagram for explaining a level drop due to undershoot. FIG. 2A is a waveform diagram showing an example of a solitary wave signal recorded on the disk 1. Symbols S1 and S2 indicate portions where the level drops due to undershoot. The forward undershoot is from the peak of the undershoot S1 to the peak point P of the solitary wave signal waveform, and here, this time is Tf. The time from the peak point P to the rear undershoot S2 is Tr.

FIG. 2B is a waveform diagram showing an example of a normal reproduced waveform. In the reproduced waveform b1, a level drop occurs at the peak point P. This is because the peak point P is ahead of the peak point f5 by the time Tf, so that the influence of the forward undershoot S1 of the peak point f5 occurs. Further, since the peak point P is located behind the peak point f1 by the time Tr, the influence of the rear undershoot S2 of the peak point f1 occurs. Therefore, a drop in amplitude occurs at the peak point P, and no signal is detected at the slice level V. That is, at the peak point of the reproduced waveform b1, a level drop occurs due to the undershoot of the peak points f1 and f5.

FIG. 2 (c) shows an example of a pulse waveform obtained by detecting the waveform of FIG. 2 (b) at the slice level V. The pulse waveform c1 is obtained by converting the reproduced waveform b1 to a slice level V
Signal is detected. A code error occurs at the peak point P due to the influence of the level drop caused by the undershoot.

The operation of the operation slice level setting means will be described with reference to FIG. Undershoot counting means 1
1 reads the solitary wave signal shown in FIG. 2A and counts the time Tf from the front undershoot to the peak point of the solitary signal waveform and the time Tr from the peak point to the rear undershoot by the reference clock. To do. When data is reproduced from the recording medium, the undershoot position detecting means 12 determines whether or not there are peaks at positions before the time Tf and after the time Tr from the respective peak points f1, f2,... In the reproduced waveform b1 reproduced from the disk 1. It discriminates the polarity and outputs an undershoot detection signal. Next, when receiving the undershoot detection signal, the slice level control means 13 sets the slice level for pulse detection low. That is, the slice level is
As shown in FIG. 2B, the slice level V is changed to the slice level V1.

Then, since signal detection is performed at the low slice level V1, no code error occurs as shown by the pulse waveform c2 in FIG. 2 (c).

A first slice level setting function for setting a slice level when the slice level control means 13 receives a first undershoot detection signal indicating that both the front of the time Tf and the rear of the time Tr have been detected. And a second slice level setting function for setting a slice level when receiving a second undershoot detection signal indicating that only one of the front of the time Tf and the rear of the time Tr is detected.

In this case, the slice level control means 13
Sets the first slice level when the first undershoot detection signal is received. When the second undershoot detection signal is received, the second slice level is set. The slice level V when the undershoot detection signal is not received is the maximum, and the second slice level (not shown) is next, which is set to a value considering only the influence of the undershoot of the front Tf or the rear Tr. The first slice level V1 is shown in FIG.
(B). Therefore, the slice level control means 13 selects and sets a plurality of preset slice levels according to the type of the undershoot detection signal.

The undershoot position detecting means 12
However, each track of the recording medium has an undershoot count function for each track for counting the time Tf from the undershoot of the isolated signal waveform to the peak point and the time Tr from the peak point to the backward undershoot of the track by the reference clock. May be. Since the reproduction waveform period is different between the inner circumference side and the outer circumference side of the disc 1, the undershoot position also differs. Therefore, by detecting the position of the undershoot for each track, the difference generated between the inner peripheral side and the outer peripheral side of the disk 1 is absorbed.

Next, an embodiment of a magnetic recording device to which the above-mentioned slice level setting device is applied will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of the magnetic recording device. The magnetic recording device includes a disk 1 which is a magnetic disk medium, a head 2 for reproducing data recorded on the disk 1, an amplifier 3 for amplifying a reproduction signal reproduced by the head, and an amplified reproduction signal for the reproduction signal. A low-pass filter 4 for waveform compensation, a delay device 5 for delaying a reproduction signal output from the low-pass filter 4 for a predetermined time, and a reproduction signal in the delay device into a pulse signal at a slice level set by a slice level setting device 14. A signal detector 6 for conversion, a data discriminator 7 for decoding the pulse signal output by the signal detector, and an interface circuit 8 for controlling data transfer of the data output by the data discriminator 7 to a host device 9. It has and.

FIG. 4 shows a disk format according to the present embodiment, in which each sector (SECT
OR), an ID portion, a solitary wave signal, and data (DA
It has been shown that the (TA) portion is arranged via a gap (GAP).

Hereinafter, this will be described in more detail. The circuit operation of the present invention and the waveforms of each part are as follows.

In the magnetic recording apparatus, when a reproduction waveform read command is received from the host device 9, the read circuit shown in FIG. 3 uses the sync (SYNC) indicating the beginning of the ID section in the disk format shown in FIG. )
Data detection is started. The ID sync data on the disk 1 is read by the head 2, amplified by the AGC amplifier 3, subjected to high-frequency noise removal and waveform compensation by the low-pass filter (LPF) 4, and then delayed by the delay unit 5 for a predetermined time. , As a read signal b.

The signal detector 6 pulsates the peak level of the waveform of the read signal b by detecting it at the slice level (reference voltage) Vs set by the slice level control means 13. The pulsed signal c is decoded into recording information by the data discriminator 7 and transferred to the host device 9 via the interface circuit 8.

When the upper device 9 completes the detection of the ID sync data, the upper device 9 outputs an ID sync data detection signal, which is input to the signal switch 10. The signal switch 10 connects the LPF 4 and the undershoot counting means 11 in synchronization with the timing at which a solitary wave signal written at a specific position on the ID section is read based on the ID sync detection signal. .

When the solitary wave signal shown in FIG. 2 (a) is input, the undershoot counting means 11 receives the time Tf from the forward undershoot to the peak point indicated by 0.
And the time T from the peak point 0 to the rear undershoot
r is counted by the reference clock T and the result is held.

When the operation of measuring and holding the time in the undershoot counting means 11 is completed, the signal switch 10 causes the connection with the LPF 4 to change from the undershoot counting means 11 to the undershoot by the reset output from the undershoot counting means 11. Switch to position detection means 12. At the same time, normal data comes to be input from the LPF 4. Signal switch 10
The undershoot position detecting means 12 is turned off at the end of data reading, that is, at the same time when the host device 9 closes the read gate.

Next, the operation at the time of reading the normal data portion will be described. Now, when there is a waveform peak P having a level drop due to an undershoot as shown by a broken line in b1 of FIG. 2 as an input signal waveform of the signal detector 6, a fixed slice level is set in the signal detector 6. When peak detection is performed at (reference voltage) V, as a detection result, an error occurs due to missing bits, as in the output pulse train indicated by c1 in FIG.

The undershoot position detecting means 12 uses the count result of the undershoot counting means 11 to determine the presence / absence of a peak at a point before the time point Tr from the peak point 0 and at a point after the time point Tf, and its polarity. Determination. When a peak P of the input signal waveform as indicated by b1 in FIG. 2 is received, the result of determination by the undershoot position detecting means 12 is that the waveform peak point P has a peak in front of Tr with the same polarity and a peak behind Tf. It has the same polarity and the result is input to the slice level control means 13.

The slice level control means 13 selects a preset slice level control voltage Vs according to the inputted discrimination result, and thereby changes the slice level in the signal detector 6 from V to V1. .
Therefore, when the peak P of the reproduced waveform delayed by a certain amount by the delay unit 5 is input to the signal detector 6, the signal is detected at the slice level V 'lower than the normal slice level V, so that the amplitude is correct. The discrimination took place,
The pulse indicated by c2 in FIG. 2 is output, and no error occurs. According to the present invention, it is possible to detect a signal in consideration of the influence of undershoot in this way.

[0039]

Since the present invention is constructed and functions as described above, according to this, even if the waveform peak of the reproduced waveform falls below the slice level for signal detection due to the effect of undershoot, the signal detection is performed. Slice level setting with an unprecedented superior effect that the error detection of information can be prevented and the reliability of the magnetic recording device can be improved by making the slice level variable for An apparatus and a magnetic recording apparatus using the same can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a slice level setting device of the present invention.

FIG. 2 is a diagram showing signal waveforms at various parts in the circuit shown in FIG. 1;

FIG. 3 is a block diagram showing an embodiment of a read circuit in the magnetic recording apparatus of the present invention.

FIG. 4 is a diagram showing a disk format in the embodiment shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 disc 2 head 3 AGC amplifier 4 low-pass filter (LPF) 5 delay unit 6 signal detector 7 data discriminator 8 interface circuit 9 host device 10 signal switch 11 undershoot counting means 12 undershoot position detecting means 13 slice level control means

Claims (4)

[Claims] 1. A solitary wave signal recorded on a recording medium is read out, and a time Tf from a front undershoot to a peak point of the isolated signal waveform and a time Tr from the peak point to a back undershoot of the solitary signal are respectively referenced. Undershoot counting means for counting by a clock; and when data is reproduced from the recording medium, presence / absence and polarity of a peak at a position before and after the time Tf from each peak point in the read reproduced waveform. A slice level comprising: an undershoot position detecting means for determining and outputting an undershoot detection signal; and a slice level control means for setting a low slice level for pulse detection when the undershoot detection signal is received. Setting device. 2. The slice level control means sets the time T
Only a first slice level setting function that sets a slice level when a first undershoot detection signal indicating that both f front and time Tr are detected is received, and only one of time Tf front and time Tr rear is provided. The slice level setting device according to claim 1, further comprising a second slice level setting function that sets a slice level when a second undershoot detection signal indicating that the signal is detected is received. 3. The undershoot position detecting means,
An undershoot count function for each track is provided for each track of the recording medium, which counts a time Tf from the front undershoot to the peak point of the isolated signal waveform and a time Tr from the peak point to the rear undershoot of the isolated signal waveform by a reference clock. The slice level setting device according to claim 1, wherein 4. A slice level setting device according to claim 1, 2 or 3, a magnetic disk medium, a head for reproducing data recorded on the magnetic disk, and an amplifier for amplifying a reproduction signal reproduced by the head. A low-pass filter for compensating the waveform of the amplified reproduction signal, a delay device for delaying the reproduction signal output by the low-pass filter for a predetermined time, and a reproduction signal in the delay device set by the slice level setting device. An interface that controls data transfer between a signal detector that converts a pulse signal at a slice level, a data discriminator that decodes the pulse signal output by the signal detector, and a host device for the data that the data discriminator outputs. A magnetic recording device comprising a circuit.