JP2696629B2 - Modulation waveform inspection method for flexible disk - Google Patents

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 An FD frequently used in information equipment is inspected at a manufacturing stage. The inspection includes a modulation inspection for amplitude fluctuation of a waveform of a recorded signal. In FIG. 3 (a), reference numeral 1 denotes an FD. Starting from an index (INDX) indicating a reference point in the rotation direction, a test of a constant amplitude V shown in FIG. The signal is written. (B) shows the envelope of the read signal, when the FD is curved, the amplitude v is periodically varied with respect to one round of the track around the average value v _m. This is usually called modulation. However, the amplitude v fluctuates aperiodically due to causes other than the bending, or +
Some are asymmetric on the side and on the-side, and these are also modulations in a broad sense. In testing, samples the read signal at appropriate time intervals T _0, by comparing the amplitude v at the sampling points in one cycle average v _m for one rotation of the track, the quality of modulation is determined. Note that for the FD modulation test, A
In NSI (American National Standards) the sampling interval T ₀ of the be 5ms is defined.

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 the speed of PM, and a test signal is written / read to / from the track of the FD 1 by the magnetic head 2.
To enter. The RC filter has a time constant of about 5 ms. The frequency component of the read signal of 200 Hz or higher is cut off, and the lower frequency component is input to the A / D converter 33 and the amplitude v is digitized. On the other hand, in response to a command from the microprocessor (MPU) 4, the timing
S sampling pulses 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 data of the sampled amplitude v is
, The one-round average value v _m is calculated and taken into the MPU 4, and the data of the amplitude v stored in the memory are compared with the average value v _m . Track 1 with a rotation speed of 300 RPM
For the circumference, sampling is performed 40 times at intervals of 5 ms.

[0004]

At present, the recording density or the 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 a 2ED type has appeared, and the recording density tends to be further improved in the future. Such a modulation test for an FD having a high recording density is not appropriate by the same method as in the past. That is, in the FD having a high recording density, the read voltage is lower than that of the conventional FD. Therefore, the high frequency component of 200 Hz or more, which has been 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 the standard is currently valid, 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,
It is another 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 for achieving the above-mentioned object, which is intended for a high recording density FD, and writes / reads a test signal to / from one round of an FD track. 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, an average value of one round of the amplitude of the read signal for one round of the track is calculated, and the average value of one round and the moving average value are compared to check the modulation of the read signal waveform. The above-mentioned minute sampling interval is set as an interval for sampling at least one thousand rounds of the track, and the moving average value is calculated for a plurality of sampling points corresponding to the sampling interval of the inspection standard. Also,
If necessary, sampling is separately performed on the + side and-side of the read signal, and the modulation on the + side and-side of the read signal waveform is examined.

[0006]

In the modulation waveform inspection method described above, the sampling interval for the read signal is such that at least one thousand rounds of the track are sampled. Further, the moving average value obtained for each sampling point is compared with the average value of one round of the track, and the waveform of the modulation is inspected. By shortening the sampling interval and comparing the moving average value for 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 the plurality of continuous sampling points is set to be the same as the sampling interval (5 ms) of the inspection condition, and satisfies the inspection standard. In addition,
If necessary, the asymmetrical modulation waveform can be inspected by separately inspecting the + side and the-side of the read signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The moving average value of a read signal according to the present invention will be described with reference to FIG. In FIG. 1, the test signal written for one round 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 (b) in the direction of the time axis t, where sampling points are p ₀ , p ₁ , p ₂ ..., And the amplitude v of the envelope sampled at each point is Here, v ₀ , v ₁ , v ₂ ... Now, the interval between the points p _{0 to} p _r is set to T ₀ (5 ms), and the respective amplitudes v _{0 to} v _r during this period are T ₀ (5 ms).
And the result is divided by the number r of points to obtain an average value v _M (# 0)
Ask for. Next, similarly, an average value v _M (# 1) for the points p _{1 to} p (r + 1) is obtained, and (# 2)...
Each average value V _M represents a so-called moving average value, which expresses a temporal change of the amplitude v in units of an interval T ₀ as a whole. In the following, the moving average value is referred to as v _M. Although the moving average value v _M does not faithfully indicate the amplitude change at each sampling point,
The change in the range of the interval T ₀ is macroscopically shown, whereby the change of the amplitude v is known more precisely than the conventional sampling of the interval T ₀ . The reason for the T ₀ and 5ms is merely to satisfy the modulation inspection standards, if shorter than 5ms if ignoring this, it is possible to obtain a more precise amplitude variation.

FIG. 2 shows a schematic block configuration of a signal processing circuit 5 for processing a modulation waveform in one embodiment of the present invention. However, as an example, a case where the positive side and the negative side of the read signal are separately tested will be described. The test signal is read by the head 2, the read signal is level-adjusted by the amplifier 51, and is input to the + side selection circuit 52a and the − side selection circuit 52b, from which the + side signal and the − side signal are output, respectively.
It is digitized by the / D converters 53a and 53b. MPU4
Of the interval ΔT (<2π
/ 1000) is output and both A /
The signal is supplied to the D converter, and thereby the peak value on the + side (+ v)
And the peak values on the negative side (−v) are sampled. The sampled + side signal is a circuit average value circuit 54a.
And a moving average value circuit 55a. The moving average value circuit 55a includes a sampling point for each of the timing pulses having an interval T ₀ (5 ms in the standard) supplied from the timing circuit. Each peak 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. On the negative side, a modulation check is performed in the same manner as described above. In the above, one cycle average value v _m and the moving average value v _M is calculated by the hard circuit, these M
Needless to say, it is also obtained by the software processing of the PU4.

[0009]

As described above, in the modulation waveform inspection method according to the present invention, a high-frequency component is detected by the shortening of the sampling interval and the moving average value for each sampling point, so that the modulation waveform is more precise than before. And, if necessary, a separate test is performed for the + and-sides of the read signal.
Asymmetrical modulation waveforms can be inspected, and the length of the moving average value is the same as the sampling interval (5 ms) of the inspection condition and satisfies the inspection standard.
This contributes to a precise inspection of a modulation waveform for a high recording density FD.

[Brief description of the drawings]

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

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

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

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

[Explanation of symbols]

DESCRIPTION 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 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 : amplitude or peak value of the read signal, v
_m : one round average value, v _M : moving average value, p ₀ , p ₁ , p ₂ ... sampling points.

Claims (3)

(57) [Claims] An object of the present invention is to write / read a test signal for one round of a track of a flexible disk having a high recording density, sample the read signal at minute intervals, and follow the sampling point. 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 obtained. And calculating a modulation of the read signal waveform by comparing the one-round average value with the moving average value. 2. The method according to claim 1, wherein the minute sampling interval is set to an interval for sampling at least one thousand rounds of the track, and the moving average value is calculated with respect to the plurality of sampling points corresponding to a sampling interval of an inspection standard. The method for inspecting a modulation waveform of a flexible disk according to claim 1, wherein the calculation is performed. 3. If necessary, the sampling is separately performed on the + side modulation and the − side modulation of the read signal, and the + side and − side modulation of the read signal waveform are inspected, respectively.
3. The method for inspecting a modulation waveform of a flexible disk according to claim 1 or 2.