JP3057281B2 - Playback waveform compensation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproduced waveform compensation circuit (a so-called time domain filter circuit) used in, for example, a floppy disk drive.

[0002]

[Prior art]

FIG. 3 shows a schematic configuration of a conventional reproduction waveform compensation circuit (hereinafter, referred to as a time domain filter circuit) used in a floppy disk drive. Note that, for example, the data is read from a floppy disk by the magnetic head 10, and
It is assumed that the waveform of the reproduced signal that has passed through the amplifier / filter 11 that performs amplification and filtering (bandpass) has a waveform W, for example, as shown in FIG.

The waveform W of the reproduced signal is obtained by a comparator 12
Sent to The comparator 12 performs zero-cross detection on the waveform W. As a result, the comparator 12 outputs a reproduced waveform P _c as shown in FIG.
Is obtained. The reproduced waveform P _c from the comparator 12
Is differentiated by a differentiator 13 of a conventional time domain filter circuit. The differentiator 13 outputs the reproduced waveform P _c
Pulse P _d as shown in FIG. 4 which corresponds to the state change is obtained. The pulse P _d is sent to the monostable multivibrator (monostable multivibrator MM) 14 as a trigger pulse.

In this monostable multivibrator 14,
Together based on the trigger pulse of the pulse P _d, the resistance R
Output waveform P _M of the resistance value and determined by the time constant based on the capacitance of the capacitor C back to a stable state after a certain time (adds a delay of a predetermined time) shown in FIG. 4 is formed.

[0006] The output waveform P _M of the monostable multivibrator 14 is sent as an inverted clock to the clock input terminal of the subsequent latch circuit 15. The input terminal of the latch circuit 15 is supplied with the reproduced waveform _Pc from the comparator 12. As a result, an output is obtained from the latch circuit 15 from which a pulse or the like contained in the reproduced waveform _Pc is removed, for example, by so-called sadling. The output of the latch circuit 15 is output from the output terminal 16 as a reproduction waveform OUT of the conventional time domain filter circuit as shown in FIG.

[0007]

If [0005] However, as a large waveform W _e of distortion as shown in FIG. 5, for example, in the comparator 12 is supplied (when distorted read waveform from the magnetic head 10), In the conventional time domain filter circuit described above, the waveform W
Zero crossing due to sadling of _e (position indicated by x in the figure)
The pulse positions of the reproduced waveform outputted from the output terminal 16, for example, the reproduction waveform OUT _e waveform become error position shifted from the position where there is originally indicated by the dotted lines in FIG. 5 occurs fear There is.

[0008] That is, by large waveform W _e of the distortion are supplied, the output becomes reproduced waveform P _ce shown in Figure 5 from the comparator 12, further the differentiator 1
The output of No. 3 is a pulse P _de as shown in FIG. In this case, in the monostable multivibrator 14 outputs a pulse P _de is supplied as a trigger pulse of the differentiator 13 in accordance with the zero-crossing (position shown in the drawing x) by Sadoringu large waveform W _e of the distortion A in FIG.
Is shortened, the capacitor C for setting the time constant cannot be sufficiently charged. For this reason, the output of the monostable multivibrator 14 becomes like the output waveform P _Me of FIG. 5 in which the delay amount in the section shown by b in the figure does not reach the above-mentioned fixed time (the original output waveform is
The metastable state must continue up to the position shown by the dotted line in the figure).

In view of the above, the latch circuit 15
Reproduced waveform even the pulse position output via an output terminal 16 from and becomes a waveform of a position shifted from the position there should originally indicated by the dotted line portion of the reproduced waveform OUT _e of FIG 5.

In the waveform diagram of FIG. 3 described above, zero crossing due to sadling occurs at the position indicated by x in the figure. In this case, since the distortion of the reproduced waveform _Pc is not so large, the zero crossing due to sadling occurs. The interval between them is widened, and the problem as in the example of FIG. 5 does not occur, and the reproduced waveform from the output terminal 16 is also good.

Accordingly, the present invention has been proposed in view of the above situation, and has as its object to provide a reproduced waveform compensating circuit which does not cause an error even if the waveform distortion is large. is there.

[0012]

SUMMARY OF THE INVENTION A reproduction waveform compensating circuit according to the present invention has been proposed to achieve the above-mentioned object, and has a reproduction waveform reproduced from a recording medium by a head and obtained by detecting a zero cross. A differentiating means for detecting a change in the state of the reproduced waveform, and a distributing means for alternately distributing the differentiated pulse output from the differentiating means into a first differentiated pulse and a second differentiated pulse. First delay pulse generating means for generating a delay pulse having a predetermined time width based on the first differential pulse, and a delay pulse having a predetermined time width based on the second differential pulse Second delay pulse generating means for generating the delay pulse, synthesizing means for synthesizing the first delay pulse and the second delay pulse, and sampling the reproduced waveform with an output pulse from the synthesizing means. Those comprising a sampling means for.

[0013]

According to the reproduced waveform compensating circuit of the present invention, the reproduced waveform is differentiated and the differentiated pulse corresponding to the state change of the reproduced waveform is alternately distributed to the first differentiated pulse and the second differentiated pulse. A delay pulse having a predetermined time width is generated from each of the first and second differential pulses and synthesized, and the reproduced waveform is sampled with the synthesized output pulse, thereby removing distortion of the reproduced waveform having large distortion ( For example, a so-called sadling error can be prevented).

[0014]

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

As shown in FIG. 1, the reproduced waveform compensating circuit of this embodiment is reproduced from a recording medium (for example, a floppy disk) by a magnetic head 10 and is provided with a comparator 1.
2. A reproducing waveform compensating circuit (time domain filter circuit) for compensating a reproducing waveform obtained by detecting a zero cross in step 2, a differentiator 13 as a differentiating means for detecting a change in the state of the reproducing waveform, A flip-flop 21 as a distributing means for alternately distributing the differentiated pulse (output pulse) output from the switch 13 into a first differentiated pulse and a second differentiated pulse, and a predetermined time based on the first differentiated pulse. A first monostable multivibrator 2 as first delay pulse generating means for generating a delay pulse having a width
2, a second monostable multivibrator 23 which is a second delay pulse generating means for generating a delay pulse having a predetermined time width based on the second differential pulse,
And an OR gate 24 as a synthesizing means for synthesizing the delayed pulse and the second delayed pulse, and a latch circuit 15 as a sampling means for sampling the reproduced waveform with the output pulse of the OR gate 24. is there.

In FIG. 1, the same components as those in FIG. 3 are denoted by the same reference numerals. Also,
In the present embodiment, a case where the waveform reproduced from the magnetic head 10 is greatly distorted is described as in FIG.

In FIG. 1, the waveform of a reproduced signal read out from, for example, a floppy disk by the magnetic head 10 and passed through the amplifier / filter 11 has a greatly distorted waveform as shown in FIG. _Suppose that it was We. That is, the zero-crossing by the so-called Sadoringu large waveform W _e of the distortion (the position shown in the figure x) was intended to have occurred.

The large waveform W _e of this strain is sent to the comparator 12, the zero-crossing by the comparator 12 is detected. Thereby, this comparator 1
From 2 (similar to the reproduced waveform P _ce in Figure 5) reproduced waveform P _ce shown in Figure 2 is obtained. The reproduced waveform _Pce from the comparator 12 is differentiated by the differentiator 13 of the time domain filter circuit of the present embodiment. Thus, from the differentiator 13, the reproduced waveform P _ce pulse P _de, as shown in FIG. 2 in accordance with the state change of the (same as pulse P _de in Fig. 5)
Is obtained. The pulse P _de is sent as an inverted clock to the clock input terminal of the flip-flop 21 of the circuit of this embodiment.

The inverted output of the flip-flop 21 is fed back to the input terminal of the flip-flop 21. The non-inverted output of the flip-flop 21 is sent to the enable terminal of the first monostable multivibrator 22, and the inverted output of the flip-flop 21 is sent to the enable terminal of the second monostable multivibrator 23. .

Further, the pulse P _de from the differentiator 13 is supplied to the first and second pair of monostable multivibrators 22 and 23 as a trigger pulse. Therefore, in the first and second monostable multivibrators 22 and 23, after a certain period of time determined by a time constant based on the pulse P _de as the trigger pulse and based on the resistance value of the resistor R and the capacitance of the capacitor C, respectively. Return to stable state (add a fixed time delay)
Output waveform P _M1 shown in FIG. 2, so that P _M2 is formed.

The output waveforms P _M1 and P _M2 of the first and second monostable multivibrators 22 and 23 are sent to input terminals of a two-input OR gate (OR gate) 24. Accordingly, the output terminal of the OR gate 24 outputs an output waveform P _OR as shown in FIG. 2 which is the logical sum of the output waveforms _{PM 1} and PM ₂ .

The output waveform P _OR of the OR gate 24 is sent to the clock input terminal of the subsequent latch circuit 15 as an inverted clock. The input terminal of the latch circuit 15 is supplied with the reproduced waveform _Pce from the comparator 12. Therefore, the latch circuit 15
Outputs a reproduction waveform OUT _S as shown in FIG.

That is, in the time domain filter circuit of this embodiment shown in FIG. 1, a pulse (differential pulse) corresponding to a change in the state of the reproduced waveform _Pce from the differentiator 13 is obtained.
The P _de is distributed to the first and second monostable multivibrators 22 and 23 by the flip-flop 21, and the first and second monostable multivibrators 22 and 23 are alternately fixed with respect to the pulse P _de . plus the time delay, the these first in OR gate 24, after synthesizing with the logical sum of the output waveform P _M1, P _M2 of the second monostable multivibrator 22, the output of the OR gate 24 By operating the latch circuit 15 to which the reproduction waveform _Pce is supplied based on the distortion, the distortion of the reproduction waveform _Pce is removed from the output of the latch circuit 15 (for example, a so-called sadling error is prevented). reproduction waveform OUT _S so obtained. In other words, according to the time domain filter circuit of the present embodiment, the section indicated by b in FIG. 5 is not affected by the size of the section indicated by a in FIG.
The reproduction waveform OUT _S is outputted from the output terminal 16 as a reproduced waveform of the time domain filter circuit of the present embodiment.

[0024]

As described above, in the reproduced waveform compensating circuit of the present invention, the reproduced waveform is differentiated and the differentiated pulse corresponding to the state change of the reproduced waveform is converted into the first differentiated pulse and the second differentiated pulse. By alternately distributing the signals, a delay pulse having a predetermined time width is generated from each of the first and second differential pulses and synthesized, and the reproduced waveform is sampled by the synthesized output pulse to thereby reduce the distortion of the reproduced waveform. It becomes possible to remove (for example, to prevent a so-called sadling error).

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a reproduction waveform compensation circuit (time domain filter circuit) according to an embodiment of the present invention.

FIG. 2 is a timing chart showing waveforms of various parts of the circuit of the embodiment.

FIG. 3 is a block circuit diagram showing a schematic configuration of a conventional time domain filter circuit.

FIG. 4 is a timing chart showing waveforms of various parts of a conventional circuit.

FIG. 5 is a timing chart showing waveforms of respective units when a distorted waveform is supplied to a conventional circuit.

[Explanation of symbols]

 10 magnetic head 11 amplifier filter 12 comparator 13 differentiator 21 flip-flop 22, 23 monostable multivibrator 24 OR gate 15 ··· Latch circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/09

Claims (1)

(57) [Claims] 1. A reproducing waveform compensating circuit for compensating a reproducing waveform obtained by detecting a zero crossing reproduced from a recording medium by a head , wherein a differentiating means for detecting a change in state of the reproducing waveform, and an output from the differentiating means. The differentiated pulse obtained is converted to the first derivative pulse.
Distributor that alternately distributes the pulse to the second differential pulse
And a delay having a predetermined time width based on the first differential pulse.
First delay pulse generating means for generating an extended pulse, and a delay having a predetermined time width based on the second differential pulse.
Second delay pulse generating means for generating an extended pulse; and synthesizing the first delay pulse and the second delay pulse.
Synthesizing means, and sampling the reproduced waveform by the output pulse of the synthesizing means.
Reproduced waveform compensation circuit characterized by comprising a sampling means for grayed.