JPS644264B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a floppy disk device, and an object of the present invention is to detect the track position of a read/write head without using an external recording device, and easily control corrective shaping of playback output. shall be.

In general, floppy disk devices record and reproduce large amounts of digital information on magnetic media, and use a writing head to record digital information on the magnetic medium in the form of two magnetic flux patterns, making it economical and efficient. In order to improve the performance, efforts are being made to record as many bits as possible per unit length of the magnetic medium to ensure reliability during reproduction. However, as is known from the past, due to the limitations of electrical and magnetic recording and reproducing devices, when the bit pulses are recorded in a manner that gradually approaches each other, it becomes more difficult to reliably reproduce the bit pulses.

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. be. One more
A limitation to one recording density is that as the number of flux changes per unit length of the medium increases, the probability of not reproducing the flux changes increases. This phenomenon is known as vanishing error.

As the density of magnetic flux changes increases, the changes representing digital information increase. In generally known digital recording devices, digital information is stored using a "nonreturn to zero method".
In this case, the non-fixed state of magnetization is given as "1" or "0". Instead, the state of magnetization is reversed each time a "1" is recorded, and maintained as is to display a magnetic recording 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. One of these results from the limited resolution of the playback device. Variations in flux reversal direction and air gaps can cause regenerated pulses to overlap other pulses or extend into the "0" region when pulses should not be regenerated. Another consequence of resolution limitations is that the reproduced signal will be large when the gap in the flux reversal direction is wide and small when the gap is narrow. Because of the limited resolution of the reproduction device, the "non-return to zero method" has difficulty detecting the presence of pulses as the number of bits recorded per unit length of the magnetic medium increases.

FIG. 4 is a diagram explaining the peak shift of the reproduction output in the "zero return method", where A is the recording signal,
B indicates the recording current, and C indicates the reproduction output. Considering the case where a pair of "1"s exist between recording signals "0", as the bit interval becomes smaller, the pulse interval b of the reproduced waveform C becomes wider than the reversal direction a of the recording current A. This deviation is called peak shift.

As mentioned above, the limit of recording density is determined by the peak shift. Therefore, as a method for improving recording density, it is important to reduce interference in the reproduced waveform, which causes peak shifts.

Many ideas have been proposed for reproduction wave correction circuits for reducing 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 f(x) as shown in FIG. 3A. On the other hand, as shown in FIG. 3B, f(t+τ) and f(t-
By creating a signal τ), adding a weight K/2 to it, and subtracting it from the input signal, a signal of equation (1) is synthesized as shown in FIG. 3C.

g(t)=f(t)-K/2{f(t+τ)+f(t-
τ)} ...(1) As a result, the tail portion of the input signal waveform is removed, and a narrowed output signal is obtained. This thinning of the reproduction output reduces interference between adjacent waveforms and eliminates phenomena such as peak shifts and peak level drops.

Such processing for modifying reproduced waves is generally referred to as read compensation or post-compensation. The constants K and τ in equation (1) are determined based on the optimum improvement effect of the actual device. Various practical circuits have also been devised, but their explanation will be omitted here.

Now, MFM is used as a double density recording method in floppy disk devices.
(MOdurated Fregueucy MODuration recording modulation method), etc., there is a limit to the recording density, as is clear from the above explanation. A floppy disk device has a rotating diskette.
Since the recording format and recording bit capacity for each track are the same, the number of recording bits per circumference increases on the inner track compared to the outer track, and the recording density is higher on the inner track, resulting in a more uneven playback waveform. becomes large, making demodulation detection difficult.
Therefore, when reading and reproducing a specific track, generally an inner periphery of the track 60, performing post-compensation (readout correction) provides a large improvement effect.

The track format of a floppy disk device consists of an index (ID) field and a data field. The index field contains information about the head position, such as the number of tracks, sectors, and sides.
If the index field is read and the position is appropriate, the data field of that sector is read and written. Also, the controller of the floppy disk device recognizes the head position based on the index information, and the number of tracks is 60.
If it is larger than the track, turn on the post-compensation signal, correct the readout and playback waveform,
If the number of tracks is smaller than 60 tracks, the post-compensation signal is turned off and the read and reproduced waveform is not corrected.

However, there is a problem in that the decision to turn on or turn off the post-compensation signal is made by reading the index field, and the information on the number of head tracks is determined based on the size of the head track (for example, 60 tracks). . That is, the index field of the inner track has a high recording density, and when reading the index field of the inner track itself, accurate information on the number of tracks cannot be obtained unless reproduction correction is performed.

The present invention provides a floppy disk device that counts track number information inside the disk device, internally controls on or off of a post-compensation signal, and easily controls correction shaping of playback output. It provides: Specifically, with track 0 as a reference, the step signal of the head movement command is measured by an up-down counter according to the polarity of the direction selection signal of the head movement command, and it is determined that the current head track position is, for example, on the inner side of track 60. A comparator detects whether the post-competition signal is on or off, and the post-competition signal is turned on or off based on this detection signal.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a diagram showing an example of an implementation circuit, and FIG. 2 is a timing chart. The write/read head moves the head position (FIG. 2A) when step signal 2 (FIG. 2B) changes from "L" to "H", ie, at the trailing edge of step signal 2. When the head direction selection signal 3 (Fig. 2C) is "H",
When step signal 2 is received in the outer circumferential direction, the head moves outward from the center of the medium. Conversely, when the head direction selection signal 3 is "L", the head moves in the inner circumferential direction, and when the step signal 2 comes, the head moves toward the center of the medium. The outermost track is the standard position track of the head and is called track 0. When the head is located on track 0, this is physically detected and a track 0 signal (FIG. 2D) is output.

As can be seen from Figure 1, the implementation circuit is composed of an IC (semiconductor integrated circuit), 4 and 4' are synchronous binary coded hexadecimal preset up/down counters, for example, SN-74191; 5' is a 4-bit comparator made of, for example, SN-7485.
Apply track 0 signal 1 to load input L to preset preset up/down counters 4 and 4'. Also, the step signal 2 is applied to the count input (CLK), and the head direction selection signal 3 is applied to the mode control input (UP/DN). When the mode control input (UP/DN) is “L”, it counts up, and conversely, the mode control input (UP/DN) is “H”
, the outputs of the preset up/down counters 4 and 4' (Q _A ,
Q _B , Q _C , Q _D ) are compared with "0011 1100" using an 8-bit comparator consisting of 5 and 5'. And the preset up/down counter output is “0011”.
1100" (60) or less, that is, the count number is 0.
to 59, the comparator output (6) becomes "H", and when the count number is 60 or more, the comparator output (6) becomes "L". Based on this output, correction control of the read and reproduced waveform is performed as post-compensation. That is, when the read track is from 0 to 59, the post-compensation signal is set to "H", that is, inactive, and when the track is 60 or more, the post-compensation signal is set to "L", that is, operated, to correct the read and reproduced waveform. .

Hereinafter, according to the present invention, the information on the number of tracks is detected based on the step signal for the head movement command, instead of reading the index field, which cannot obtain accurate information on the number of tracks on the inner track.
In high-density recording and playback, it is possible to easily determine whether the number of tracks in the head is on the inner or outer side compared to a limited number of tracks (for example, 60 tracks) without using an external recording function. It is possible to realize a floppy disk device that can perform correction control and read accurate data.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of a floppy disk device showing an embodiment of the present invention, FIG. 2 is a timing chart thereof, FIG. 3 is a principle diagram of waveform correction using a cosine equalizer, and FIG. The figure is a diagram illustrating the peak shift of the reproduced output in the zero return method. 1...Track 0 signal, 2...Step signal,
3... Head direction selection signal, 4, 4'... Preset up/down counter, 5, 5'... Comparator.

Claims (1)

[Claims] 1. A means is provided for detecting whether the write/read head is on the inner or outer side of the limited track position based on the head movement command step signal, and the correction shaping of the read waveform is controlled by the output from the means. A floppy disk device characterized by: