JPS6131524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a floppy disk device, which has a simple configuration, detects the track position of a read/write head without using an external recording device, and controls corrective shaping of playback output. The purpose is to make it easy.

Generally, a floppy disk device records and reproduces large amounts of digital information on a magnetic medium, and the digital data is recorded on the magnetic medium by a write head in the form of two magnetic flux patterns. usually,
At least one of these magnetic flux patterns is
The flux changes either with a complete reversal of polarity or from one level of magnetization to another.

In addition, temporal fluctuations between devices that record digital information and devices that reproduce it, changes in the speed of the medium,
Because of the occurrence of flux, clock pulses are used to read data from magnetic media.

On the other hand, in order to improve economy and efficiency, as many pits as possible are recorded per unit length of the magnetic medium as long as reliability during reproduction allows. Furthermore, due to the limitations of electrical and magnetic recording and reproducing devices, it becomes more difficult to reliably reproduce bit pulses that are recorded closer together. One of the limitations of such recording density is that as the recording density increases, the number of magnetic flux patterns per unit length on the magnetic medium also increases, and therefore the number of magnetic flux changes per unit length also increases. It is. The read head therefore has an output that is proportional to the rate of change of magnetic flux in the magnetic medium. Therefore, each flux reversal is
The reproduction head reproduces it as a pulse. As recording density increases, the distance between reproduced pulses decreases. As a result, the wavelength decreases and the frequency of the reproduced signal increases accordingly.

Another limitation on recording density is that as the number of flux changes per unit length of the medium increases, the likelihood of not reproducing the flux changes increases. This phenomenon is known as vanishing error. For example, erasure occurs when the wavelength of the recorded pulse approaches the gap width of the read head. As the density of magnetic flux changes increases, the changes representing digital information increase.

Digital information in commonly known digital recording devices is stored using a "nonreturn" method.
If we consider the "to zero" method), the non-fixed state of magnetization is given to "1" or "0". Instead, the state of magnetization is reversed each time a "1" is recorded,
It is maintained as it is to display a magnetic record of "0". Therefore, it can be seen that one flux reversal is required each time a "1" appears, and no flux reversal is required for a "0". Therefore, a serious problem arises as the recorded magnetic flux reversals become closer together, that is, as the density becomes higher. This one is
arises from the limited resolution of the playback device. That is, variations and air gaps between flux reversals can cause regenerated pulses to overlap other pulses or extend into the "φ" region when pulses should not be regenerated. Another consequence of resolution limitations is that the reproduced signal will be large when the gap between flux reversals is wide and small when the gap between flux reversals is narrow. Therefore, since the "non-return to zero method" has a limit to the resolution of the reproducing device, it becomes difficult to detect the presence of pulses as the number of bits recorded per unit length of the magnetic medium increases.

Figure 1 explains the peak shift of the reproduction output in the non-zero return method. Considering the case where there is a pair of "1"s between signal "0"s, as the bit interval becomes smaller, the recording current decreases. Reversal interval a
The pulse interval b of the reproduced waveform becomes wider. This deviation is called peak shift. As the recording density increases,
The thickness d of the medium and the head gap length q significantly affect bit interference, resulting in a large peak shift. The normalized response of the pulses of the two reproduced waveforms due to mutual interference is generally expressed by the first equation.

FIG. 2 is an example of calculation using the first equation, and is a reproduced waveform obtained by superimposing two pulse waveforms.

As mentioned above, the limit of recording density is determined by the peak shift. Therefore, as a method for improving recording density, it is necessary to reduce the interference in the reproduced waveform that causes peak shifts. Many reproduction wave correction circuits have been proposed to reduce this reproduction wave interference.

As an example, the principle of waveform modification using a cosine equalizer will be explained with reference to FIG. Assume now that the input signal waveform is represented by a time function (x).
On the other hand, (t+τ) and (t-
τ), and set the weight to k/
By adding 2 and subtracting it from the input signal, the signal of the second equation is synthesized.

g(t) = (t) - k/2 {(t + τ) + (t - τ)} ...(2) As a result, the tail part of the input signal waveform is removed,
A refined output signal is obtained. By narrowing the playback output waveform, interference between adjacent waveforms is reduced,
Phenomena such as peak shift and peak level drop can be removed.

Such a procedure for modifying the reproduced wave is generally called read compensation or post-compensation.

The constants k and τ in equation (2) are determined based on the optimum improvement effect of the actual device. Various practical circuits have also been devised, but their explanations will be omitted here.

Now, MFM is used as a double density recording method in floppy disk devices.
(Modulated Frequency Maduration recording modulation method), etc., there is a limit to the recording density, as is clear from the above explanation. In a floppy disk device, the diskette rotates, and the recording format and recording bit capacity for each track are the same, so the number of recording bits per circumference increases on the inner track compared to the outer track. The inner track has a higher recording density, and the reproduced waveform becomes more distorted, making it difficult to detect demodulation. Therefore, when reading out and reproducing a specific track, which is generally inner than the track 60, performing post-compensation (readout correction) provides a large improvement effect. The track format of a floppy disk device consists of an ID (index) field and a data field. Information regarding the head position, such as the number of tracks, number of sectors, and number of sides, is written in the index field. If the ID field is read and the position is appropriate, the data field of that sector is read and written.

Based on the ID information, the controller side of the floppy disk device recognizes the head position, and if the number of tracks is greater than 60, it turns on the post-compensation signal and corrects the readout and playback waveform. If it is small, the post-compensation signal is turned OFF and the readout and playback waveform is not corrected. However, there is a problem in that the decision to turn on or off the post-compensation signal is made by reading the ID field and determining whether the head track number information is larger or smaller than a specific track (for example, 60 tracks). There is. In other words, the inner track
The ID field has a high recording density, and when reading the ID field itself of the inner track, accurate track number information cannot be obtained unless reproduction correction is required.

The present invention not only detects the head track position using software from the read data of the track format, but also detects the head position of the floppy disk device by physical means, and uses this detection result to correct and shape the read wave. By doing this, the above problems can be solved. As a means for detecting whether the head position is on the inner or outer periphery of a specific track position, for example, by regulating the amount of movement or positioning of the shaft that drives and supports the head, the belt that drives the head, etc. It can be achieved.

FIG. 4 shows an example of this, and 1
2 is a cover, 3 is a head, 4 is a head carriage, 5 is a protrusion provided on a part of the head carriage 4, and 6 is an optical or mechanical means for detecting that the protrusion 5 approaches as the head carriage 4 moves. This sensor detects when the head 3 reaches position 60 on the track. 7 continues to operate based on the output of the sensor 6 while the head 3 is on the inner periphery of the track 60, corrects the waveform of the signal read out by the head 3, and when the head 3 is located on the outer periphery of the track 60. A readout reproduction waveform correction section cancels the correction, and 8 is a reproduction output terminal.

As explained above with reference to the embodiments, according to the present invention, the position of the head is physically detected, and based on this, it is determined whether or not to correct the reproduced waveform. Regardless of the situation, highly accurate playback output can always be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the peak shift of the reproduced output in the non-zero return method, Fig. 2 A and B are explanatory diagrams of the reproduced waveform obtained by superimposing two pulse waveforms, and Fig. 3
The figure is an explanatory diagram of the principle of waveform modification using a cosine equalizer. FIG. 4 is a schematic diagram of a floppy disk device according to an embodiment of the present invention. 1...Tail socket, 3...Head, 4...Head cartridge, 5...Protrusion piece, 6...Sensor, 7
...Reading reproduction waveform correction section.

Claims (1)

[Claims] 1 means for detecting movement of the write/read head or its head carriage, which operates when said head is located on the inner circumferential side of a certain track;
A floppy disk device equipped with means for correcting the waveform of a readout signal from a head.