JPH0135421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a method for tracking a read signal from a data carrier and a device for implementing this method. The invention is particularly applicable to reading magnetic disks belonging to a disk memory device in a data processing device.

In current data processing devices, there is a tendency for magnetic disk memory devices to be used more frequently. The reason is that such magnetic disks
The memory device has a high storage capacity, and from the time when the data processing device receives an access instruction for a certain required data item,
This is because it takes a relatively short amount of time for a magnetic read/write head to access an item of data stored anywhere on the disk.

As is well known, magnetic disks store data in encoded form on concentric recording tracks having a width of less than 1/2 to 300 mm on both sides. These recording tracks are identified by being assigned a sequential number j (j is an integer) from 0 to (N-1). Note that N is the total number of recording tracks. The encoded representation of the serial number j for one recording track is called an address. The most frequently used codes are binary codes. Generally, only one read head is provided for each side of the disk.

As is well known, in the case of a memory device with a small storage capacity consisting of only one or two disks, the addresses of tracks on one side of the disk are recorded on the same side. A maximum amount of space is made available for recording the data processed by the data processing device to which the disk memory belongs, and a minimum amount of space is made available in connection with this disk surface. It is used to record addresses and data for servo-controlling the position of the magnetic head relative to the track. This data (address, position control data) is generally referred to as track position designation data.

According to current practice, track position data is recorded in reference zones distributed over the entire surface of the disk. In this case, the number of zones is at least equal to the number of tracks, and index means are provided for making it possible to detect the position of the start of each zone. Each track has at least one zone associated with it.

Each reference zone has a plurality of individual cells, each cell storing at least one item of track location data.

In order to record a series of data items on a magnetic disk, a series of small magnetic domains called "element magnets" are generated along each track of the disk, these magnetic domains are distributed over the entire length of the track, and It is known that the magnetic induction is in a direction parallel to the surface of the disk, but with successive opposite magnetization directions. That is, the direction of magnetization of each domain is opposite.

Also, as is well known, the term "bit" means binary "1".
or "0" digit, and the representation of the digit takes the form of an analog or theoretical electrical signal. Here, an analog signal has two limit values, one of which is generally positive and the other negative.
A logic signal is defined as a signal that has a voltage that varies between two values, while a logic signal is a signal that can only take on two values, referred to as a "logic zero" and a "logic one."

The data cells placed in each track are then formed by changing the magnetization direction.

When a magnetic read head associated with one side of the disk encounters a series of variations in magnetization direction corresponding to a reference zone, the head generates a series of analog signals which are converted into logic pulses by a shaping circuit. formatted into. The beginning of the reference zone is indicated by a special pulse.

As is well known, signals generated by a magnetic head associated with one side of the disk corresponding to track position data are transmitted to a device for positioning the head on the disk. This device not only moves the head radially from track A, where it is initially located, to position it on track B from which data is to be read, but also moves the magnetic head during the time it takes to read data from track B. This makes it possible to accurately center and hold the track B on this track B. In order to be able to read the data from track B read by the head as quickly as possible and with maximum accuracy, the time required to move the head from track A to track B must be as short as possible and It is important that the head is centered on track B with as much accuracy as possible. In order to satisfy these two conditions, it is necessary to detect analog signals corresponding to variations in the magnetization direction in the reference zone with maximum accuracy. In view of this, the signal is preferably rejected unless it reaches a certain threshold or predetermined level. According to current practice, this threshold is relatively low, approximately 20 to 25% of the maximum amplitude that can be reached by the analog signal generated by the head.

"beginning or initial portion of a reference zone" means the data in the zone that is first read out in time by a read head associated with a given side of the disk when that side of the disk passes the read head; It is a collection of items. Similarly, the "remainder of a zone" is the set of data items within a zone that are chronologically last read by the head. Generally, the number of data items stored at the beginning or beginning of a zone is less than the number of data items stored in the remainder of the zone. It should also be noted that magnetic read heads are often commonly referred to as "read transducers."

The purpose of the invention is to maintain constant the average level of a signal read from coded information stored on a data carrier such as a magnetic disk;
and a signal that allows the detection threshold used for the read signal to be adjusted as a function of the actual level of the signal, the signal being made to follow the amplitude of the read signal from the above information. This is an attempt to provide a method for this to occur.

The present invention also seeks to provide a read signal tracking adjustment device for implementing the above method.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1a one of the sides of the magnetic disk D is shown. The disk D rotates in the direction of arrow F and its available recording area is divided into circles d1 and d.
2. On this surface, there is a circle S ₀ ,...
n sectors S _i ,...S _o are defined. 1st
As can be seen more clearly from figure b, each sector S _i is divided into two parts SDO _i and SAD _i , one of which is divided by the data processing unit to which the disk Meri belongs. On the other hand, track addresses and data necessary for servo-controlling the position of the magnetic head T with respect to the track axis A _xj are recorded.

The area of part SAD _i is much smaller than the area of part SDO _i . Figures 1c and 1d are enlarged views of the portion SAD _i of sector S _i contained within circle c.

Each SAD _i part of sector S _i has N zones ZRP _ip ,
...ZRP _ij , ...ZRP _i(N-1) , and these zones are called position reference zones. For simplicity, five zones ZRP _IP or
Only ZRP _i4 is illustrated as a rectangle.

The boundary between the various zones ZRP _ij is the circular axis A _xj of the magnetic track. Sequential number j with axis A _xj
Each magnetic track in has an associated zone ZRP _ij
have. That is, track O has zone ZRP _ip , track 1 has zone ZRP _i1 correlated,
The same applies below.

Each zone ZRP _ij is such that the beginning of the zone stores the sequence of data items needed to servo control the position of the read head and the remainder of the zone contains the address of the track associated with this zone, i.e. a sequential number. It is arranged to store the bits forming the address of track j.

On one side there is associated a reading head T ₁
It is assumed that a reading head _T2 is provided on the other side and associated with it on the other side. Generally, the data read by heads T ₁ and T ₂ are not simultaneously received by the read circuit of the disk memory belonging to magnetic disk D. That is, the reading circuit first accepts the data read by head _T1 , and then
Accepts data read by T ₂ .
The operation of switching from accepting data read by head _T1 to accepting data read by head _T2 in this manner is called "head selection switching."

The read head can occupy two positions. One of the positions is a rest position where no data can be detected and therefore no analog read signal can be generated, and the other position is where the head is located a few microns from the disk and no data can be detected. is a read position at which a read signal can be generated that can be detected and used by the read circuit.

Figures 2a to 2c are illustrations of the manner in which a desired track within a data carrier may be addressed in accordance with the present invention. Here, track 1
24, 125 and 126 are taken as examples, and the corresponding zones ZRP _i124 , ZRP _i125 and ZRP _i126 contain address data. and each zone has a first part and a second part.
The first part includes six cells C ₁ to C ₆ , and
Included in the second part are C ₁ ′ to C ₉ ′.

Contained in the six cells C ₁ to C ₆ in the first part are precision position servo control information, each cell containing two transitions.
The first one of them is positive (+) and the second one is negative (-). The first transition is the servo control information, and is the position P ₁ (for even zones, ie, for ZRP _i2 , ... ZRP _i124 , ZRP _i126 ...) or the position P ₂ (for odd zones). For,
That is, with respect to ZRP _i1 , . . . ZRP _i125 , . On the other hand, the second displacement is always negative and is always located at position P ₃ , no matter what the reference zone is. This also means adjustment fluctuations (or
It is also called a marker.

The address bits in the second part are
C ₁ ′ to C ₉ ′, each of these cells containing a single transition. That is, cell C ₁ ′,
Cells C ₃ ′, C ₅ ′, C ₇ ′, and C ₉ ′ contain positive transitions, and cells C ₂ ′, C ₄ ′, C ₆ ′, and C ₈ ′ contain negative transitions.
Then, in each of the cells C ₁ ′ to C ₉ ′, a corresponding transition will be placed at one of the two predetermined positions P ₁ or P ₂ . Here, the address bit at _P1 is "0" and the address bit at _P2 is "1".

Note that these address bits are written in Gray code.

Now, in FIG. 2a, when the head T is placed on the center of the track 124 (two zones
When straddling ZRP _{i 124} and ZRP _{i 125} ), the read signal from head T appears as shown in Figure 2b. and the corresponding address/
The bits are divided into two threshold values S ⁺ and S ^-
(Fig. 2c).

FIG. 3 illustrates the basic principle of the device according to the invention.

The device comprises a magnetic read/write head _T1 connected to an amplifier circuit A.

The output terminal of the amplifier circuit A is connected to the memory circuit M.

The output of the circuit M is connected to a generator G which generates two detection thresholds S ⁺ , S ^- having mutually equal but opposite signs and to a circuit C for comparison with a reference signal V _ref . ing. The output of circuit C is connected to amplifier circuit A by a follow-up feedback loop R.

FIG. 4 is a simplified circuit diagram of one embodiment of a device according to the invention, illustrating a first mode of operation when a voltage is applied.

In FIG. 4, reference numeral 1 represents the winding of the magnetic read/write head connected to the amplifier circuit 2. In FIG.

Read signal generated from amplifier circuit 2
SRVBAS is applied to memory circuit 3. This circuit 3 has a storage capacitor 4 connected in parallel to two series resistors 5 and 6. A switch 7 controlled by the signal PKENB* is inserted into this π-shaped circuit.

A shunt switch 8 controlled by the signal FASTGC* is connected in parallel with the resistor 6. The output signal MRKPK from the circuit 3 is compared in a comparator amplifier 9 with the reference signal V _ref .

Note that this reference signal V _ref is a certain predetermined DC voltage, which is determined experimentally, and is normally operated on its linear operating characteristic curve. Comparison - made taking into account the technical characteristics of the amplifier 9. For this purpose, the six signals G ₁ to G ₆ included in MRKPK are designed to approximately have a predetermined average value. This average value is independent of variations in the output signal of the head T, properties of the disk magnetic layer, amplifier gain, etc. However, during each rotation of the disk, the value of MRKPK may vary to some extent from its average value because the surface of the magnetic medium is not completely flat. This is because there may be some disadvantages regarding variations in the movement of the heads on the disk.

The signal MRKPK is also fed to a generator 10 which generates detection thresholds S ⁺ and S ^- .

Amplifier 9 generates an error signal PKERR,
This error signal PKERR passes through a filter 11 and then is applied to a switch 1 controlled by a signal MAXGN.
2 is applied to the control gate of the field effect transistor 13 connected to the amplifier circuit 2.

The output signal MRKPK from circuit 3 is the reference signal V _ref
, and an error signal PKERR is generated as a result. The voltage of signal PKERR is filtered by filter 11 and controls the gate of field effect transistor 13 (signal GNCTRL). This transistor 13, connected as a variable resistor, acts on the gain of the read amplifier 2.

The circuit detects the peak values MRKPK of the signals corresponding to the first six adjustment fluctuations (referred to as markers - Figure 6a) in the zone ZRP _ij currently being read out.
Detect. On the other hand, the signal SRVWND must be equal to "logic 1" (read position data).
The time constant of the circuit 3 during this detection operation is, for example, as follows. That is, the charging time constant=TO=0.2 μs and the discharging time constant T1=0.01 ms.

Here, the charging circuit is formed by a diode (no symbol) in the memory circuit 3 and a capacitor 4, and the discharging circuit is formed by a resistor 5 (or a resistor 6).
connected in series) and a capacitor 4. Usually, the effective resistance value when the charging circuit is formed is different from the effective resistance value when the discharging circuit is formed, so there is a difference between the charging time constant and the discharging time constant. will occur.

The peak value MRKPK is stored at least for the time required to read out all of the information (including address bits) contained in the second part of the reference zone _{ZRP_ij} .

According to the circuit of the invention, this peak value is compared with a reference signal V _ref and an error signal PKERR is generated by a comparison amplifier 9 therefor. After filtering by a filter 11, this error signal PKERR is transmitted to a transistor 13 (signal GNCTRL) which controls the gain of the reading circuit.

Due to the filtering effect of the filter circuit 11, for example, 6
The device is stabilized at a frequency of Hz. This cut
The off frequency was chosen because it is not possible to correct for amplitude fluctuations during the time it takes for the disk to rotate once, ensuring a correct average level.

The level of the useful signal read out from zone ZRP _ij can vary by +20% from the above average level.

Therefore, in order to eliminate the disturbance caused by the shortfall due to such fluctuations, the signal MRKPK is used to detect the bits forming the track address.
Two thresholds S equal to +75% of the signal
Each zone is generated by generator 10 using MRKPK.
Generated every ZRP _ij .

In this way, the thresholds S ⁺ and S ^- are made to track the peak value of the signal to be decoded.

FIG. 6 shows the read signal SRVBAS. The first part of this signal is during the period when the enable or enable signal SRVWND is equal to "logic 1".
This is a signal portion corresponding to position data.

This first part is followed by a second part which stores the track address. During this second portion, signal SRVWND is equal to "logic 0".

When this second part is read, the signal
Thresholds S ⁺ and ^S- are generated based on MRKPK.

Figure 6a shows the zones of head position data.
During the period from the time when the first marker G1 in ZRP _ij appears to the time when the sixth marker G6 (corresponding to the sixth adjustment fluctuation) appears, the peak value
It is shown how MRKPK is configured step by step.

At the end of the position data zone, the signal SRVWND inverts to "logic 0" (Figure 7) and the signal
Generates PKENB*.

The peak value of the signal MRKPK is thus determined by the first marker of the next zone ZRP _ij (SRVWND again "logic 1") closes the switch 7,
It is stored in capacitor 4 until detection of the peak value of MRKPK is possible again.

[Brief explanation of drawings]

1a to 1d are illustrations of one of the known methods of data distribution on the surface of a magnetic disk, and FIGS. 2a to 2c are embodiments of the invention for addressing a desired track of a data carrier. FIG. 3 is a block diagram schematically illustrating the overall configuration of the device according to the invention; FIG. 4 is a circuit diagram showing one embodiment of the device according to the invention in one mode of operation; FIG. is an exemplary diagram when the apparatus of FIG. 4 is in the second operating mode; FIG. 6 is an exemplary diagram of threshold generation when decoding a track address; and FIG. FIG. 7 is a waveform diagram showing the formation of the signal MRKPK. FIG. 7 is a timing chart of various signals related to the operation mode in the device of the present invention. 1...Read/write head, 2...Amplification circuit, 3
...memory circuit, 4...storage capacitor, 5, 6...resistor, 7, 12...switch, 8...shunt switch,
9... Comparison amplifier, 10... Generator, 11... Filter, 13... Field effect transistor, 15... Monostable flip-flop, 16... NAND gate, 1
7, 18, 21...bistable flip-flop, 1
9...Inverter, 20...Counter.

Claims (1)

[Scope of Claims] 1. A method for reading data with a transducer from reference zones recorded in tracks on a data carrier, each track containing one reference zone, the reference The zone includes a plurality of initial cells, each of the initial cells being adapted to undergo a magnetic flux variation, and when the magnetic flux variation of the initial cell is read by the transducer, a first the initial cell is followed by a plurality of data cells, each of the data cells is configured to have a magnetic flux variation, and the magnetic flux variation of the data cell is configured to generate a waveform; When read by the transducer, the first waveform and the second waveform of the reference zone are adapted to generate a second waveform, the first waveform and the second waveform of the reference zone being
detecting the peak amplitude of the first waveform, which normally has substantially the same peak amplitude, at least over the period of time required to read the waveform of the data cell in the reference zone; , accumulating the detected peak amplitude; a threshold for the level of a waveform from the data cell, the threshold varying depending on the detected and accumulated peak amplitude of the first waveform; of,
deriving in response to the detected and accumulated peak amplitude, and defining a value for each data cell in response to the waveform of each data cell after qualifying the waveform by the threshold; The aforementioned method comprising: 2 A device for reading data from reference zones recorded on tracks on a data carrier, each track containing one reference zone, the reference zone having a plurality of initial cells. the initial cell is configured to undergo a magnetic flux variation, and the initial cell is configured to generate a first waveform when the magnetic flux variation of the initial cell is read by a transducer; is configured to track a plurality of data cells having magnetic flux fluctuations, and to generate a second waveform when the magnetic flux fluctuations of the data cells are read by the transducer, the first and second waveforms have substantially the same peak amplitude; detecting the peak amplitude of the first waveform in response to the first and second waveforms; means for accumulating the detected peak amplitude over a period at least equal to the period required for reading out the waveform in the cell; deriving a threshold for the level of the second waveform in response to the accumulated peak amplitude; means for determining the threshold value, wherein the threshold value varies depending on a peak amplitude detected for the first waveform; and after the threshold value is subjected to a thresholding process, each 3. The apparatus as described above, comprising: means for defining a binary value for each data cell in response to the amplitude of the data cell waveform. 3. for controlling the amplitude of a waveform whose peak amplitude is detected prior to said second waveform being read out from a track during a period in which a transducer deriving a signal is precisely positioned in said reference zone; 3. Apparatus according to claim 2, further comprising means.