JP2528180Y2 - Time margin evaluation device for magnetic disk drives - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for evaluating a time margin of a magnetic disk device such as a floppy disk, a hard disk, or the like.

[Prior Art] FIG. 4 shows a configuration example of a conventional time margin evaluation device.

In FIG. 1, reference numeral 1 denotes a magnetic disk reproduced by a magnetic disk device. The magnetic disk 1 is recorded in advance with a recording current of a rectangular wave having a duty of 50% and a constant period (2 to) (shown in FIG. 5A).

A signal (waveform shown in FIG. 1B) reproduced from the magnetic disk 1 by the reproducing magnetic head 2 is amplified by the reproducing amplifier 3 and then supplied to the peak detector 4.

The peak detector 4 outputs peak detection pulses PPD respectively corresponding to the positive peak and the negative peak of the reproduced signal.
(Shown in FIG. 4C), and the peak detection pulse P
The PD is supplied to a time interval analyzer (hereinafter referred to as “TIA”).

Time Tn between each peak detection pulse PPD in TIA5 is measured, a plurality, frequency distribution is created for example 10 ⁶ with a time data, which is displayed on the display unit (not shown).

This frequency distribution is a substantially normal distribution as shown in FIG. 6, for example. Then, by the user's operation, the peak shift | to-to '| serving as the evaluation data of the time margin and the standard deviation σ related to the jitter are calculated and displayed. For example, the calculation of the peak shift | to-to '| is performed by designating the peak position to' of the distribution, and the calculation of the standard deviation σ is performed by designating the distribution range.

[Problems to be Solved by the Invention] By the way, for example, in a disk device adopting the DC erasing method, the time from the positive peak to the negative peak and the time from the negative peak to the positive peak of the reproduction signal are different. As a result, the frequency distribution has two peak positions ta and tb as shown in FIG. That is, two normal distributions overlap each other. One of the causes is that magnetization erasure is performed with one magnetic pole biased.

As described above, even when the distribution has two peak positions ta and tb, the peak shifts | to−ta | and | to−tb | can be calculated by designating the peak positions ta and tb of the distribution. And the calculation of the standard deviation σ can be performed by specifying the distribution range.

However, since the two normal distributions overlap as described above, the peak positions ta and tb are also different from the normal distribution peak positions, and the peak shifts | to−ta | | to−tb | and the standard deviation σ are not accurate values.

Therefore, in this invention, even if the time from the positive peak to the negative peak of the reproduced signal is different from the time from the negative peak to the positive peak, the peak shift and the standard that become the evaluation data of the time margin are obtained. This allows the deviation to be accurately calculated.

[Means for Solving the Problems] This invention reproduces a signal in which a positive-side peak and a negative-side peak alternately appear at predetermined time intervals from a magnetic disk, and the reproduced signal has a positive-side peak and a negative-side peak, respectively. Pulse generating means for generating corresponding first and second pulses, a first time from the first pulse to the second pulse, and a second time from the second pulse to the first pulse , And processing means for separately calculating the frequency distribution of the plurality of first times and the plurality of second times measured by the time measuring means.

[Operation] According to the above-described configuration, the peak shift and the standard deviation are calculated based on the frequency distribution created at a plurality of first times from the positive-side peak to the negative-side peak, and the negative-side peak to the positive-side The peak shift and the standard deviation are calculated based on the frequency distribution created at a plurality of second times up to the peak.

In other words, even if the time from the positive peak to the negative peak of the reproduced signal is different from the time from the negative peak to the positive peak, the peak shift is performed based on the distribution in which the two normal distributions overlap. And the standard deviation is not calculated, so that the calculation can be performed accurately.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG.
(Represented by a waveform in FIG. 2A) is amplified by a reproduction amplifier 3 and supplied to a peak detector 4. The peak detector 4 outputs peak detector pulses PPD corresponding to the positive peak and the negative peak of the reproduced signal, respectively.
(Shown in FIG. 5B), and this peak detector pulse PPD is supplied to OR circuits 11 and 12.

The output signal of the amplifier 3 is supplied to a comparator 13 having a hysteresis characteristic. From the comparator 13, the pulse P having a high level “H” during the period from the positive peak to the negative peak of the reproduced signal and a low level “L” during the period from the negative peak to the positive peak is obtained.
CM (shown in FIG. 4C) is output, and this pulse PCM is supplied to the input terminals A2 and B1 of the selector 14.

The pulse PCM output from the comparator 13 is supplied to the inverter 15 and the phase is inverted. The pulse PCM '(shown in FIG. D) output from the inverter 15 is
It is supplied to the input terminals A1 and B2 of the selector 14.

Select signal SSEL is applied to select terminal SEL of selector 14.
Is supplied. In the A mode in which the select signal SSEL is set to the high level "H", the input terminals A1 and A1
The signal supplied to A2 is output to output terminals Y1 and Y2, respectively, while the signal supplied to input terminals B1 and B2 is output to output terminal Y1 in the B mode in which select signal SSEL is at low level "L". And output to Y2.

The signals obtained at the output terminals Y1 and Y2 of the selector 14 are
The signals are supplied to OR circuits 11 and 12, respectively. The output signals of the OR circuits 11 and 12 are supplied to the A-side and B-side input terminals of the TIA 5, respectively. In TIA5, the time from the pulse supplied to the A-side input terminal to the pulse supplied to the B-side input terminal is measured. Other operations are the same as those of TIA5 in the example of FIG.

In the above configuration, in the A mode, the selector
Pulses PCM 'and PCM are output from the fourteen output terminals Y1 and Y2, respectively. Therefore, a pulse PPDA (illustrated in FIG. 2E) corresponding to the positive peak of the reproduced signal (illustrated in FIG. 2A) is output from the OR circuit 11, and is supplied to the A-side input terminal of the TIA5. The OR circuit 12 outputs a pulse PPDB (shown in FIG. 5F) corresponding to the negative peak of the reproduced signal, and supplies this to the B-side input terminal of the TIA5.

Therefore, in TIA5, the pulse PPDA is changed to the pulse PPDB.
Time to, i.e. to the negative side peak from the positive electrode side peak of the reproduction signal time ··, Tn-4, Tn, Tn + 2, ·· is measured, a plurality, for example, the frequency distribution is generated with a time data ¹⁰⁶ in This is displayed on a display unit (not shown). This frequency distribution is a substantially normal distribution as shown in FIG. 3A, for example. Then, a peak shift | to-ta 'serving as time margin evaluation data is performed by a user operation.
| And the standard deviation σ related to the jitter are calculated and displayed.

In the B mode, the output terminal Y1 of the selector 14
And Y2 output pulses PCM and PCM ', respectively. Therefore, the pulse PPDB corresponding to the negative peak of the reproduction signal is output from the OR circuit 11, and this is the TIA5
Is supplied to the input terminal on the A side. The OR circuit 12 outputs a pulse PPDA corresponding to the positive peak of the reproduced signal, and supplies the pulse PPDA to the B-side input terminal of the TIA5.

Therefore, in TIA5, the pulse PPDB is changed from the pulse PPDB.
, That is, the time from the negative peak to the positive peak of the reproduced signal,..., Tn−3, Tn−1, Tn + 1,.
There is measured a plurality, frequency distribution is created with a data example ¹⁰⁶ in time, which is displayed on the display unit (not shown). This frequency distribution is a substantially normal distribution as shown in FIG. 3B, for example. And, by user operation,
Peak shift | to-t that becomes evaluation data of time margin
b ′ | and the standard deviation σ related to the jitter are calculated and displayed.

Thus, in this example, in the A mode, the time from the positive peak to the negative peak of the reproduced signal,.
4, Tn, Tn + 2,... Are measured, the peak shift and the standard deviation are calculated based on the frequency distribution created by the time data, and the time from the negative peak to the positive peak in the B mode is calculated. , Tn-3, Tn-1, Tn +
Are measured, and the peak shift and the standard deviation are calculated based on the frequency distribution created by the time data.

Therefore, according to the present example, even if the time from the positive peak to the negative peak of the reproduced signal is different from the time from the negative peak to the positive peak, the distribution in the state where the two normal distributions overlap is different. , The peak shift and the standard deviation can be calculated more accurately than the conventional example.

In the above-described embodiment, the TIA5 measures the time from the pulse supplied to the input terminal on the A side to the pulse supplied to the input terminal on the B side. Selector if possible
The part 14 can be omitted. In that case, TIA5
, A select signal SSEL is supplied as a switching signal.

[Effects of the Invention] As described above, according to the invention, the peak shift and the standard deviation are calculated based on the frequency distribution created at a plurality of first times from the positive peak to the negative peak. At the same time, the peak shift and the standard deviation are calculated based on the frequency distribution created in a plurality of second times from the negative peak to the positive peak, so that the time from the positive peak to the negative peak of the reproduced signal is calculated. Even when the time from the negative peak to the positive peak becomes different, the peak shift and the standard deviation can be accurately calculated based on the distribution in which the two normal distributions overlap. Therefore, by using the evaluation device of the present invention, the time margin of the disk device can be more accurately evaluated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the embodiment, FIG. 4 is a block diagram of a conventional example, and FIGS. FIG. 1 magnetic disk 2 reproduced magnetic disk 4 peak detector 5 time interval analyzer 11, 12 OR circuit 13 comparator 14 selector 15 inverter

Claims (1)

(57) [Scope of request for utility model registration] A signal is reproduced from a magnetic disk in which a positive peak and a negative peak alternately appear at predetermined time intervals, and a first pulse and a second pulse corresponding to the positive peak and the negative peak of the reproduced signal, respectively. Pulse generating means for generating two pulses; and time measuring means for measuring a first time from the first pulse to the second pulse and a second time from the second pulse to the first pulse. A time margin evaluation device for a magnetic disk device, comprising: a processing unit for separately calculating and processing frequency distributions of a plurality of first times and a plurality of second times measured by the time measurement unit.