JPH0589455A - Modulation waveform inspecting method for flexible disk - Google Patents

Abstract

PURPOSE:To detect a high frequency component so as to inspect precisely a modulation waveform, and simultaneously, to inspect an asymmetrical waveform as well by the shortening of a sampling interval and a moving average value for each sampling point. CONSTITUTION:A read-out signal from a head 2 is level-adjusted by an amplifier 51, and is digitized by A/D converters 53a, 53b through a (+)-side and a (-)-side selection circuits 52a, 52b. The sampling pulse of an interval AT is given from a timing circuit 56 to the converters 53a, 53b in accordance with the command of an MPU 4, and peak values +V, -V are sampled, and are transferred to one-round average circuits 54a, 54b and moving average circuits 55a, 55b. A one-round average value and the moving average value are calculated, and are fetched to the MPU 4 through an interface 42, and the one-round average value is stored once in a memory 41, and the modulation of a read-out signal waveform is inspected by the processing of the MPU 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a modulation waveform in an FD (flexible disk).

[0002]

2. Description of the Related Art FDs often used in information equipment are inspected at the manufacturing stage. Tests include modulation tests for amplitude fluctuations in the waveform of the recorded signal. Reference numeral 1 in FIG. 3 (a) indicates an FD, and a test of a constant amplitude V shown in (a) of FIG. 3 (b) is performed for one turn of the track 1a, starting from an index (INDX) indicating a reference point in the rotation direction. The signal is written. (B) shows the envelope of the read signal, and when the FD is curved, its amplitude v periodically fluctuates for one round of the track with the average value v _m as the center. This is commonly called modulation. However, the amplitude v fluctuates aperiodically due to causes other than bending, or +
Some sides are asymmetrical with respect to the other side, and these are also modulations in a broad sense. In the inspection, the read signal is sampled at an appropriate time interval T ₀ , and the amplitude v at the sampling point is compared with the one-round average value v _m for one round of the track to judge whether the modulation is good or bad. For the FD modulation test, A
The NSI (American standard) stipulates that the sampling interval T ₀ be 5 ms.

FIG. 4 shows a conventional modulation inspection circuit 3
The schematic configuration of is shown. FD1 is 300R by driver
The magnetic head 2 rotates at a speed of PM, a test signal is written / read to / from the track of the FD 1, the read signal is level-adjusted by an amplifier 31, and the RC filter 32 is used.
To enter. The RC filter has a time constant of about 5 ms, the frequency component of 200 Hz or higher of the read signal is cut, and the component of less than that is input to the A / D converter 33 to digitize the amplitude v. On the other hand, 5 m from the timing circuit 34 according to a command from the microprocessor (MPU) 4.
Sampling pulses at s intervals are input to the A / D converter,
The data of the amplitude v is sampled, taken into the MPU 4, and stored in the memory (MEM) 41. At the same time, the sampled amplitude v data is transferred to the average value circuit 35.
, The one-cycle average value v _m is calculated and taken into the MPU 4, and the data of the amplitude v stored in the memory is compared with this. In addition, the track 1 of the rotation speed of 300 RPM
Sampling is performed 40 times at intervals of 5 ms with respect to the circumference.

[0004]

Now, at present, the recording density or recording capacity of the FD is 1 MB (megabyte).
As described below, recently, a high recording density of 4 MB and a large capacity called 2ED type have appeared, and there is a tendency for the recording density to further improve in the future. The modulation inspection for the FD having such a high recording density is naturally not appropriate by the same method as the conventional method. That is, in the FD of high recording density, since the read voltage is lower than that of the conventional one, the high frequency component of 200 Hz or higher cut by the conventional inspection method lowers the S / N ratio of the signal and causes an error. There are many dangers. Therefore, it is necessary to inspect even high frequency components. However, it is necessary at the same time to satisfy this condition, since any standard will be valid at the moment even if it is revised. The present invention has been made in view of the above, and can inspect even high-frequency components of a read signal,
Moreover, it is an object of the present invention to provide a modulation inspection method that satisfies a sampling interval of inspection conditions.

[0005]

SUMMARY OF THE INVENTION The present invention is a modulation waveform inspection method that achieves the above object, and is intended for an FD having a high recording density, and a test signal is written / read to / from one round of a track of the FD. Then, the read signal is sampled at minute intervals. An average value for each amplitude of the read signal at a plurality of sampling points subsequent to the sampling point is sequentially calculated for each sampling point to obtain a moving average value. At the same time, a one-cycle average value of the read signal amplitude for one track is calculated, and the one-cycle average value is compared with the moving average value to inspect the modulation of the read signal waveform. The above-mentioned minute sampling interval is set as an interval at which one round of the track is sampled at least 1,000 times, and the moving average value is calculated for a plurality of sampling points corresponding to the sampling intervals of the inspection standard. Also,
If necessary, the + side and-side of the read signal are separately sampled, and the modulation for the + side and-side of the read signal waveform is inspected.

[0006]

In the above-mentioned modulation waveform inspection method, the sampling interval for the read signal is at least 1,000 times for one round of the track. Further, the moving average value obtained at each sampling point is compared with the one-round average value of the track to inspect the modulation waveform. By shortening the sampling interval and comparing the moving average value with respect to each sampling point, the high frequency component of the read signal is detected and the modulation waveform is inspected in more detail than before. Further, the length of a plurality of consecutive sampling points is the same as the sampling interval (5 ms) of the inspection condition, and satisfies the inspection standard. In addition,
If necessary, the asymmetric modulation waveform can be inspected by separately inspecting the + side and-side of the read signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The moving average value of read signals in the present invention will be described with reference to FIG. In FIG. 1, the test signal written for one turn of the track is read / read by the magnetic head 2 to obtain the read signal (a). On the other hand, one round (2π) of the track is sampled at least 1000 times by the sampling pulse of the sampling interval ΔT (<2π / 1000). (B) shows the envelope of the read signal obtained by enlarging (A) in the direction of the time axis t, the sampling points are p ₀ , p ₁ , p ₂ ... And the amplitude v of the envelope sampled at each point is Let v ₀ , v ₁ , v ₂ ... Now, the interval between the points p _{0 to} p _r is T ₀ (5 ms), and the amplitudes v _{0 to} v _r in the meantime.
Are summed, and this is divided by the number r of points to obtain an average value v _M (# 0)
Ask for. Next, similarly, when the average value v _M (# 1) for the points p _{1 to} p (r + 1) is obtained, and subsequently (# 2) ...
Each average value v _M represents a so-called moving average value, which represents the temporal change of the amplitude v as a unit of the interval T ₀ as a whole. In the following, the moving average value is v _M. The moving average value v _M does not faithfully show the amplitude change of each sampling point,
The change in the range of the interval T ₀ is shown by a macro, so that the change of the amplitude v is known more precisely than the conventional sampling of the interval T ₀ . The reason why T _{0 is set} to 5 ms is simply to satisfy the modulation inspection standard. If this is ignored and shortened to 5 ms or less, the amplitude change can be obtained more precisely.

FIG. 2 shows a schematic block configuration of a signal processing circuit 5 for processing a modulation waveform according to an embodiment of the present invention. However, as an example, a case where the + side and the − side of the read signal are inspected separately is shown. The test signal is read by the head 2, and the read signal is level-adjusted by the amplifier 51 and input to the + side selection circuit 52a and the − side selection circuit 52b, and the + side signal and the − side signal are respectively output from A and A.
It is digitized by the / D converters 53a and 53b. MPU4
Commanded by the timing circuit 56, the interval ΔT (<2π
/ 1000) sampling pulse is output and both A /
It is given to the D converter, and by this, the peak value (+ v) on the + side
The peak values (-v) on the negative side and the negative side are sampled. The sampled + side signal is the one-cycle average value circuit 54a.
To the moving average value circuit 55a. In the moving average value circuit, in the moving average value circuit, a plurality of consecutive samplings including a sampling point are provided for each timing pulse having an interval of T ₀ (5 ms in the standard). Each crest value of the signal at the point is added and divided by a plurality to calculate a moving average value (+ v _M ). This together with one round average value by one round averaging circuit (+ v _m) are calculated, both data of the moving average value (+ v _M) and one round average value (+ v _m) is taken into MPU4 via an interface (INT) 42 is further one round average value (v _m) is temporarily stored in the memory 41, the modulation of the processing of the MPU + side of the read signal waveform is examined. The same processing is performed on the − side in parallel with the above, and the modulation inspection is performed. In the above, the one-cycle average value v _m and the moving average value v _M are calculated by the hardware circuit.
Needless to say, it is also required by the software processing of PU4.

[0009]

As described above, in the modulation waveform inspecting method according to the present invention, the sampling interval is shortened and the moving average value for each sampling point is used to detect a high-frequency component, so that the modulation waveform is more accurate than before. , And if necessary, the + and-sides of the read signal are separately inspected,
Asymmetrical modulation waveforms can be inspected. Furthermore, the length of the moving average value is the same as the sampling interval (5 ms) of the inspection conditions and satisfies the inspection standard.
This contributes to precise inspection of the modulation waveform for FD with high recording density.

[Brief description of drawings]

FIG. 1 shows an explanatory diagram of a moving average value of a read signal according to the present invention.

FIG. 2 is a schematic block configuration diagram of a signal processing device according to an embodiment of the present invention.

[Fig. 3] (a) shows a flexible disk (FD),
(b) shows envelopes of the write test signal and the read signal, respectively.

FIG. 4 shows a schematic block diagram of a conventional modulation inspection circuit.

[Explanation of symbols]

1 ... Flexible disk (FD), 1a ... Track, 2 ... Magnetic head, simply head, 3 ... Conventional modulation inspection circuit, 31 ... Amplifier, 32
... RC filter, 33 ... A / D converter, 34 ... Timing circuit, 35 ... Average value circuit, 4 ... Microprocessor (MPU), 41 ... Memory (ME
M), 42 ... Interface (INT), 5 ... Signal processing circuit, 51 ... Amplifier, 52b ... + side selection circuit,
52 b ... - side selection circuit, 53a, 53b ... A / D converter, 54a, 54b ... 1 round average value circuit, 55a, 55b ... moving average circuit, 56 ... timing _{circuit, v, v 1, v 2} , v _r ... read signal amplitude or peak value, v
_m ... 1 lap average value, v _M ... moving average _{value, p 0, p 1, p} 2 ... sampling points.

Claims (3)

[Claims] 1. A flexible disk having a high recording density is targeted, a test signal is written / read to / from one track of a track of the flexible disk, the read signal is sampled at minute intervals, and the sampling point is continued. An average value for each amplitude of the read signal at a plurality of sampling points is sequentially calculated for each sampling point to obtain a moving average value, and an average value of the amplitude of the read signal for one round of the track is calculated. Is calculated, and the modulation value of the flexible disk is inspected by comparing the one-cycle average value with the moving average value to inspect the modulation of the read signal waveform. 2. The minute sampling interval is defined as an interval at which one round of the track is sampled at least 1,000 times, and the moving average value is with respect to the plurality of sampling points corresponding to the sampling interval of the inspection standard. The method for inspecting the modulation waveform of a flexible disk according to claim 1, which is calculated. 3. If necessary, the sampling is separately performed for the + side modulation and the − side modulation of the read signal, and the + side and − side modulation of the read signal waveform is inspected, respectively.
The modulation waveform inspection method for a flexible disk according to claim 1.