JPH06243596A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To quicken the establishment of synchronization of the device and also to make the device always normally operated. CONSTITUTION:A synchronizing pattern obtained by making a pattern of a fourth order M group formed by a magnetic disk 1 is detected by a synchronizing pattern detector 8 from an output of a magnetic head 2, and based on the output of the synchronizing pattern detector 8, the synchronization is established.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing device such as an optical disc device, a magneto-optical disc device or a magnetic disc device for recording / reproducing information (data) on a recording medium such as an optical disc, a magneto-optical disc or a magnetic disc. .

[0002]

2. Description of the Related Art In a conventional magnetic disk device, for example,
A so-called self-synchronous disk device that generates a clock signal from the reference signal (preamble) recorded on the magnetic disk or the data string itself when writing data, and from a synchronization pattern that is physically or magnetically preformed on the magnetic disk. There is a so-called external synchronous disk device that generates a clock.

Of the self-synchronous disk device and the external synchronous disk device, for example, the external synchronous disk device can record and reproduce data on the magnetic disk 21 as shown in FIG. ing.

The magnetic disk 21 has tracks divided into a plurality of sectors, and each sector is composed of a plurality of segments. Each segment is basically divided into a data area for recording data and a servo area for recording servo control signals.

The servo areas are formed at equal intervals on the order of several hundreds to several thousands, and among them, the servo areas of about 50 to 100 arranged at equal intervals are
A synchronization establishment pattern, a clock pattern, an access pattern, and a fine pattern are formed. A phase synchronization pattern is formed in one of the 50 to 100 servo areas instead of the synchronization establishment pattern.

Hereinafter, the synchronization establishing pattern will be referred to as a unique pattern, and the phase synchronizing pattern will be referred to as an index pattern.

In other servo areas, patterns other than the above unique patterns, that is, a clock pattern, an access pattern, and a fine pattern are formed.

These patterns are formed by removing unnecessary portions of the magnetic layer 21b formed on the substrate 21a by etching or the like. And
Each of these patterns is DC magnetized in the lateral direction (track direction).

The unique pattern is radially formed on the magnetic disk 21, and when the device is started up or is out of synchronization due to external vibration or the like, approximate synchronization is performed before accurate synchronization is performed by the clock pattern. This is a pattern for applying (initial synchronization) (a pattern for establishing synchronization).

The index pattern is the magnetic disk 2
This pattern gives the origin of 1 (position of phase 0), and is basically used for controlling the eccentricity of the magnetic disk 21.

The clock pattern is radially formed on the magnetic disk 21, and a clock required for recording / reproducing data to / from the data area can be generated with reference to the position of the clock pattern. There is.

The access pattern is a pattern that defines a position in the radial direction of the disk used when a predetermined track is accessed by a seek operation, and its length is changed in the tracks within a predetermined range. There is.

The fine pattern is a pattern for tracking control. This fine pattern is X, Y,
Four types of A and B are provided. The pattern X is provided so as to face the track n and every other track (tracks n ± 2, n ± 4, ...) From the track n. On the other hand, the pattern Y has the track n.
Are provided so as to face the tracks n ± 1, n ± 3, ...

The pattern A is formed at a position where the pattern X is moved to the inner peripheral side by 1/2 track pitch. The pattern B is formed at a position where the pattern Y is moved to the inner peripheral side by 1/2 track pitch.

In the external synchronous disk device, when the magnetic disk 21 is rotated and each pattern passes over the magnetic head, an isolated waveform on the pulse is output from the magnetic head at the leading edge and the trailing edge of each pattern. The servo control signal is generated based on the output timing of this isolated waveform.

[0016]

The conventional unique pattern or index pattern is a 15-bit pattern such as 110000000001100 or 110000000001111 as shown in FIG. 11, for example.

That is, the unique pattern and the index pattern cannot appear in the data recorded in the data area, the clock pattern in the servo area, the access pattern, or the fine pattern. Is a pattern in which nine 0s continue. The unique pattern or index pattern is the last 2 bits (LSB and
The second bit from the LSB) is set to 00 or 11 so that each can be distinguished.

In the conventional external synchronous disk device, when detecting the unique pattern and the index pattern, first, nine consecutive 0's are detected between 1's and 1's.

Therefore, for example, 9 consecutive between 1 and 1
When an error (extra bit error) in which one of the two 0s is erroneously detected as 1 occurs, the unique pattern and the index pattern are not detected, and the magnetic disk 2
It was impossible to perform initial synchronization or control the eccentricity of the magnetic disk 21 until 1 rotates and the next unique pattern and index pattern are detected.

That is, as described above, the unique pattern and the index pattern are patterns in which the number of 0's that cannot appear in the data recorded in the data area, the clock pattern in the servo area, the access pattern, or the fine pattern is continuous. Therefore, there is a problem that extra bit errors occur with a certain probability, and it takes time before initial synchronization can be applied and eccentricity of the magnetic disk 21 can be controlled.

Further, one of the unique pattern or index pattern, for example, at the beginning or end of the pattern
Error that is erroneously detected as 0 (missing bit error)
When the error occurs, a 15-bit bit string deviated by several bits from the position on the magnetic disk 21 where the unique pattern or index pattern is recorded may be erroneously detected as the unique pattern or index pattern.

In this case, initial synchronization is applied or eccentricity of the magnetic disk 21 is controlled based on the erroneously detected bit string of 15 bits, which causes a problem that the device does not operate normally. .

As described above, the unique pattern and the index pattern are the last 2 bits of the 15 bits.
Since only the bits are different, there is a problem that they are easily erroneously detected as the other pattern.

Further, when the recording density of the magnetic disk 21 is increased, the above-mentioned extra bit error and missing bit error occur more frequently, and there is a problem that the probability that the device does not operate normally increases.

The present invention has been made in view of such a situation, and speeds up the establishment of synchronization of the device, and
This is to ensure that the device always operates normally.

[0026]

According to a first aspect of the present invention, there is provided a recording / reproducing apparatus in which a magnetic disk 1 as a recording medium on which a synchronizing pattern formed by patterning a PN series is formed, and information is recorded on the magnetic disk 1. Based on the output of the magnetic head 2 as a recording / reproducing means for reproducing, a synchronizing pattern detector 8 as a detecting means for detecting a synchronizing pattern from the output from the magnetic head 2, and an output of the synchronizing pattern detector 8. It is characterized by including a timing generating circuit 9 or a position control circuit 11 as a synchronizing means for applying the.

A recording / reproducing apparatus according to a second aspect of the present invention is characterized in that the synchronization pattern is a pattern of M series of PN series.

According to a third aspect of the recording / reproducing apparatus, the synchronization pattern has first and second synchronization patterns such as a unique pattern and an index pattern, and the unique pattern or the index pattern is
It is characterized by patterning different M series.

According to a fourth aspect of the recording / reproducing apparatus, the unique patterns or the index patterns have the same sequence length.

According to a fifth aspect of the recording / reproducing apparatus, the M sequence is generated from a linear feedback shift register circuit represented by a reciprocal irreducible polynomial.

According to a sixth aspect of the recording / reproducing apparatus, the unique pattern is a synchronization establishment pattern for establishing synchronization, and the index pattern is a phase synchronization pattern for achieving phase synchronization. .

In the recording / reproducing apparatus according to the seventh aspect, the synchronization pattern detector 8 matches the same pattern as the unique pattern or the index pattern obtained by patterning the M series with the output from the magnetic head 2. When the number of matched bits is equal to or more than a predetermined number of detected bits, a detection signal indicating that the unique pattern or the index pattern is detected from the output from the magnetic head 2 is output, and the unique pattern or the index pattern is formed. The predetermined number of detection bits is changed based on the autocorrelation of each M sequence.

In the recording / reproducing apparatus according to the eighth aspect, the synchronization pattern detector 8 matches the same pattern as the unique pattern or the index pattern obtained by patterning the M series with the output from the magnetic head 2. When the number of matched bits is equal to or larger than a predetermined number of detected bits, a detection signal indicating that a unique pattern or an index pattern is detected from the output from the magnetic head 2 is output, and before the synchronization is established. It is characterized in that the predetermined number of detection bits is changed later.

A recording / reproducing apparatus according to a ninth aspect is characterized in that the recording medium is the magnetic disk 1 and the recording / reproducing means is the magnetic head 2.

[0035]

In the recording / reproducing apparatus having the above-mentioned structure, the synchronizing pattern detector 8 detects the synchronizing pattern formed on the magnetic disk 1 and which is a pattern of the PN series, from the output of the magnetic head 2 for synchronizing. Pattern detector 8
Synchronization is established based on the output of Therefore, so to speak, a pattern of a PN sequence having a strong autocorrelation is detected as a synchronization pattern, so that an erroneous detection of the synchronization pattern is prevented, the synchronization of the device is quickly established, and the device is always in a normal state. It can be operated.

When the synchronization pattern is a pattern of the M sequence of the PN sequence, this synchronization pattern can be easily generated.

The synchronization pattern includes first and second synchronization patterns such as a unique pattern and an index pattern, and when the unique pattern or the index pattern is a pattern of different M series, it is unique. It is possible to prevent the pattern and the index pattern from being erroneously detected as the other pattern.

The unique pattern is a synchronization establishment pattern for establishing synchronization, and the index pattern is
In the case of a phase synchronization pattern for achieving phase synchronization, it is possible to quickly establish synchronization and achieve phase synchronization.

The synchronization pattern detector 8 matches the same pattern as the unique pattern or the index pattern obtained by patterning the M series with the output from the magnetic head 2, and the number of matched bits is a predetermined number of detected bits. When the above is the case, a detection signal indicating that a unique pattern or an index pattern has been detected from the output from the magnetic head 2 is output, and
In the case of changing the predetermined number of detection bits based on the autocorrelation of each of the M sequences forming the unique pattern or the index pattern, the unique pattern and the index pattern can be easily detected.

The sync pattern detector 8 matches the unique pattern or the index pattern, which is a pattern of the M series, with the output from the magnetic head 2, and the number of coincident bits is a predetermined number of detected bits. When the above is the case, a detection signal indicating that a unique pattern or an index pattern has been detected from the output from the magnetic head 2 is output, and
In the case of changing the predetermined number of detection bits before and after synchronization is established, the predetermined number of detection bits should be made smaller after synchronization is established, as compared with before synchronization is established. Therefore, the unique pattern and the index pattern can be easily detected.

[0041]

FIG. 1 is a block diagram showing the configuration of an embodiment of a magnetic disk device to which the recording / reproducing apparatus of the present invention is applied. The magnetic disk 1 has a format as shown in FIG. 2, and the unique pattern and the index pattern have strong autocorrelation, for example, M series (Maximam Leng).
The configuration is the same as that of the conventional magnetic disk 21 shown in FIG. 10 except that the th Shift Register Sequence) is patterned.

The magnetic disk 1 has, for example, a fourth-order M
A unique pattern and an index pattern in which the sequence is patterned are formed.

Now, the M series will be described. First,
A finite field of order q is represented by GF (q), which is composed of an adder on GF (q), a k-stage 1-time-slot delay element, and a coefficient unit, and has no adder between stages, If the circuit in which the taps are fed back to the first stage through the adder is a linear feedback shift register circuit (FIG. 3), the linear feedback shift register circuit regards the coefficient of the polynomial on GF (q) as a time series, and It can be expressed by a polynomial like. H (x) = h ₀ + h ₁ x + h ₂ x ² + ... + h _k x ^k (1) where h _i εGF (q) (i = 0, 1, ..., k)

In FIG. 3, h _k = 1 (h _k
∈ GF (q), h _k ⁻¹ ∈ GF (q),
By multiplying both sides of equation (1) by h _k ⁻¹ , equation (1) can be made into a polynomial with a maximum coefficient of 1, that is, a monic polynomial. Represents a feedback shift register circuit).

When the coefficient h ₀ of the coefficient unit in the linear feedback shift register circuit of FIG. 3 is not 0, n is H (x)
, A binomial expression x that can be divided without leaving a remainder
^When the minimum order is ⁿ −1, the output of the linear feedback shift register circuit has a cycle of n.

Further, in this case, in a coset ring of a polynomial ring modulo x ⁿ -1, the ideal generated by G (x) represented by the following equation (set of polynomial multiples of G (x))
The basis vector of the vector space created by is one cycle of the output of the linear feedback shift register circuit. G (x) = ( ^xn- 1) / H ⁺ (x) (2) However, H ⁺ (x) is a reciprocal polynomial of H (x) (H ⁺
(X) = x ⁿ H (x ^-1 )).

The sequence with the maximum period that can be obtained from the linear feedback shift register circuit having such a k-stage 1-time-slot delay element is a k-order M sequence. That is, if H (x) is a primitive irreducible polynomial of degree k, then H (x)
The output of the linear feedback shift register circuit represented by (x) is a k-th order M sequence.

In the present specification, the M series is treated as a two-dimensional series, that is, a series whose components are 0, 1 (εGF (2)).

The k-th order M sequence has the following properties.

(C1) ... Cycle (sequence length of one cycle) n is 2 ^k −1 (C2) ... M series of one cycle (a ₀ , a ₁ , ..., A)
_n (= 2 ^k −1) patterns of length k (a _j , a _{j + 1} , ..., a _{j + k−1} ) starting from any of
All the patterns of length k except the pattern of all 0s (k is 0 pattern) appear once (where j =
0, 1, ..., N-1). (C3) ... One-cycle M sequence is composed of 2 ^k-1 -1 0s and 2 ^k-1 1s. (C4) ... The number of M sequences that are essentially different except for the phase shift is equal to the number of primitive irreducible polynomials of order k. (C5) ··· 1 cycle of M series, x ^ ideal generated by the (2 ^k -1) modulo ^{(x ^ (2 k -1)} -1) / H + (x) make vector It can be obtained as a space basis vector. Note that x ^ (2 ^k -1) is
It means x 2 ^k −1. H ⁺ (x) is H
It means the reciprocal polynomial of (x).

The fourth-order M series as the index pattern or unique pattern of the magnetic disk 1 of FIG.
It is generated from a linear feedback shift register circuit represented by a quartic primitive irreducible polynomial of the following equation (3) or equation (4). H ₁ (x) = 1 + x ³ + x ⁴ (3) H ₂ (x) = 1 + x + x ⁴ (4)

A primitive irreducible polynomial of degree 4 is, for example, "P
As described in eterson and Weldon, "Error Correcting Codes" and the like, it is known that there are only the above two equations and they are mutually reciprocal (become reciprocal polynomials). Therefore, equations (3) and (4) are both reciprocal irreducible polynomials as well as primitive irreducible polynomials.

As shown in FIG. 4, the linear feedback shift register circuit expressed by the equation (3) has four delay circuits x _{4 to} x ₁ and outputs of the delay circuits x ₁ and x _{4 which} are vertically connected. Is added (XOR of the outputs of the delay circuits x ₁ and x ₄ ) and output to the delay circuit x ₄ . In this linear feedback shift register circuit, the initial values (x ₄ , x ₃ , x ₂ , x ₁ ) of the delay circuits x _{4 to} x ₁ are all other than 0, for example (1, 0, 0, 0). Then,
The value latched by the delay circuit x ₄ to _{x 1 (x 4, x 3} ,
x ₂ , x ₁ ) changes as follows.

That is, (1,0,0,0) → (1,1,0,0) → (1,1,1,0)
→ (1,1,1,1) → (0,1,1,1) → (1,0,1,1) → (0,1,0,1) → (1,
(0,1,0) → (1,1,0,1) → (0,1,1,0) → (0,0,1,1) → (1,0,0,1)
→ (0,1,0,0) → (0,0,1,0) → (0,0,0,1) → (1,0,0,0) → ・ ・
・ (Repeat thereafter)

The output of the linear feedback shift register circuit is
The value latched in the delay circuit x ₁ , that is, the value on the rightmost side in the parentheses in the values latched by the delay circuits x _{4 to} x ₁ described above, therefore, in this case, 000111101
Thus, a fourth-order M sequence with 011501 15 bits as one cycle is obtained.

Similarly, from the linear feedback shift register circuit (not shown) expressed by the equation (4), if the initial value is (1, 0, 0, 0), 00010011
A fourth-order M sequence having 0101111 as one cycle is obtained.

Even when the property (C5) of the M-sequence is followed, the same M-sequence as in the case described above can be obtained.

That is, (x ^ (2 ^k −1) −1) / H ⁺ (x) in the property (C5) of the M sequence described above, k to 4 and H ⁺ (x) to When calculated in place of (4) of H ₂ (x) of the reciprocal polynomial H ₂ ⁺ (x), reciprocal polynomial of H ₂ (x), since an H ₁ of the formula (3) (x), ( x ^ (2 ⁴ -1) -1) / H ₂ ⁺ (x) = (x ¹⁵ -1) / H ₁ (x) = (x ¹⁵ -1) / (1 + x ³ + x ⁴ ) = x ¹¹ + x ¹⁰ + X ⁹ + x ⁸ + x ⁶ + x ⁴ + x ³ +1 and the basis vector of the four-dimensional vector space created by the ideal generated by the above equation is {1 + x ³ + x ⁴ + x ⁶ + x ⁸ + x ⁹ + x ¹⁰ + x ¹¹ } → (100110101111000 ^{) {x (1 + x 3} + x 4 + x 6 + x 8 + x 9 + x 10 + x 11)}
^{→ (010011010111100) {x 2 (} 1 + x 3 + x 4 + x 6 + x 8 + x 9 + x 10 + x 11)} (001001101011110) {x 3 (1 + x 3 + x 4 + x 6 + x 8 + x 9 + x 10 + x 11)} (000100110101111) Becomes

Therefore, from the primitive irreducible polynomial of equation (4), 100110101111000 (0100110)
10111100, 001011101011110,
Alternatively, a fourth-order M sequence with one cycle of (000100110101111) is obtained.

That is, in this case, one cycle of the M series 00 obtained by setting the initial value as (1, 0, 0, 0) from the linear feedback shift register circuit expressed by the equation (4).
0100110101111 is cyclically replaced by 3 to 0 bits to the left (shifted to the left by LS and
B sequence is replaced with MSB, or right bit shifted and MSB is replaced with LSB. M sequence 100110101111000, 01
001101011100, 00100110101
1110 or 000100110101111 is obtained (the k-th order M sequence is, as described above,
Since it has a period of 2 ^k −1, even if the M sequence of one period is cyclically replaced, it does not become an M sequence different from the original M sequence, but the same M sequence).

Next, the M sequence {a _j } (j
= 0, 1, ..., N−1: n is the autocorrelation function P (s) of the period of the M sequence (sequence length of one period) P (s) = Σa _{j + s} a _j (however, Σ changes j from 0 to n−1, and
_{j + s} a _j ), which means that the autocorrelation function P (s) is a sequence obtained by shifting the M sequence by s bits (bit-shifted) and the original M sequence. It indicates how many bits match.

Here, it is assumed that 0 is before and after the M sequence {a _j } (a _j in the range of j <0 or j> n−1). Therefore, when the autocorrelation function P (s) is calculated, a _{j + 1} , a _{j + 2} , ..., A _{j + of} the sequence {a _{j + s} } obtained by shifting the M sequence by s bits are used. and _{s, a 0, a 1,} ···, a s-1 of the original M-sequence {a _j} is
The product (AND) with 0 will be taken.

The number of bits in which the sequence obtained by shifting (bit-shifting) the M sequence by 1 bit or more matches the original M sequence is M
The self-correlation function P (s) of the M-sequence that is sufficiently smaller than the sequence length of the sequence, that is, s is not 0, is sufficiently smaller than the auto-correlation function P (0) of the M-sequence in which s is 0, and the M-sequence is Known as a strong line.

Further, the total sum of the autocorrelation function P (s) of the M series becomes a constant value even if the M series is cyclically replaced.
The shape of the autocorrelation function P (s) (how the value changes) is M
It becomes different when the sequence is cyclically permuted. That is, by cyclically permuting the M sequence, for example, P (1) to P (3) or P (-1) to P (-3) of the autocorrelation function P (s) of the original M sequence are obtained. Compared and cyclically substituted M
Of the autocorrelation functions P '(s) of the sequence, P' (1) to P '(3) or P' (-1) to P '(-3) may be smaller.

That is, when the M series is cyclically replaced, the original M series is shifted by 1 to 3 bits (bit-shifted).
Compared to the number of bits in which the sequence matches the original M sequence, the number of bits in which the cyclically permuted M sequence is shifted (bit-shifted) by 1 to 3 bits (bit-shifted) matches the original permuted M sequence. May be sufficiently small.

Therefore, in the present embodiment, P of the autocorrelation function P (s) is included in the fourth-order M series obtained based on the equation (3) and the M series obtained by cyclically permuting the M series. (1) to P (3) and P (-1) to P (-3)
The smaller one is used as the index pattern of the magnetic disk 1.

Therefore, the 15-bit pattern obtained by patterning the fourth-order M series 101011001000111 obtained based on the equation (3) is used as the index pattern of the magnetic disk 1 as shown in FIG. Is laterally magnetized.

Here, 4 as an index pattern
The autocorrelation of the next M-sequence 101011001000111 is shown in FIG.

Further, in the present embodiment, P of the autocorrelation function P (s) is included in the M-sequence of the fourth order obtained based on the equation (4) and the M-sequence obtained by cyclically permuting the M-sequence.
(1) to P (3) and P (-1) to P (-3) are smaller, and the cross-correlation with the M sequence as the index pattern is weak (M as the index pattern.
The sequence and its M sequence were shifted (bit-shifted)
The number of bits that matches the bits of the series is small) is used as the unique pattern of the magnetic disk 1.

Therefore, the 15-bit pattern obtained by patterning the fourth-order M series 100110101111000 obtained based on the equation (4) is used as the unique pattern of the magnetic disk 1 as shown in FIG. 5 (b).
Is laterally magnetized.

Here, FIG. 7 shows the autocorrelation of the fourth-order M series 100110101111000 as a unique pattern, and further, the fourth-order M series 101011001000111 as an index pattern and the fourth-order M series 10011010111100 as a unique pattern.
The cross-correlation with 0 is shown in FIG.

By using the fourth-order M series having strong autocorrelation as the unique pattern and the index pattern of the magnetic disk 1, the position on the magnetic disk 1 where the unique pattern or the index pattern is recorded is used. In a 15-bit bit string deviated by several bits from, the number of bits matching the actual unique pattern or index pattern is very small, so that a 15-bit pattern adjacent to the unique pattern or index pattern on the magnetic disk 1 is , A unique pattern or an index pattern is prevented from being erroneously detected.

Further, by using two M series having weak cross-correlation as the unique pattern or the index pattern of the magnetic disk 1, the unique pattern and the index pattern may be erroneously detected as different patterns from each other. To be prevented.

Therefore, the initial synchronization and the phase synchronization can be quickly applied.

Next, returning to FIG. 1, the magnetic head 2 has a VC
The position is controlled to a predetermined position by the position control circuit 11 via M12, and a predetermined track of the magnetic disk 1 is accessed.

The recording data generating circuit 6 operates in synchronization with the clock from the clock generating circuit 10, converts the input data into recording data, and the recording amplifier 7 and switch 3
It is configured to output to the magnetic head 2 via the contact point R of.

The data reproduced from the magnetic disk 1 by the magnetic head 2 is the contact P of the switch 3 and the reproduction amplifier 4.
The data is supplied to the data demodulation circuit 5, the synchronization pattern detector 8, the clock generation circuit 10, and the position control circuit 11 via the. The data demodulation circuit 5
It operates in synchronization with the clock from the clock generation circuit 10, demodulates the input data and outputs it.

The synchronization pattern detector 8 receives the input data and the unique pattern (10011010) described above.
1111000) or index pattern (101
011001000111) and stores the same unique standard pattern or index standard pattern, respectively, and matches each standard pattern with the input data in bit units (ANDs the standard pattern with the input data in bit units). ), Unique patterns and index patterns. Then, the synchronization pattern detector 8 generates a synchronization auxiliary signal or a phase synchronization auxiliary signal for applying initial synchronization or phase synchronization, respectively, based on the timing at which the unique pattern or the index pattern is detected, and the timing generation circuit 9, Output to the position control circuit 11.

The clock generation circuit 10 generates a clock from the data input from the reproduction amplifier 4 and outputs this clock to the recording data generation circuit 6, the data demodulation circuit 5 and the timing generation circuit 9. The timing generation circuit 9 generates various timing signals based on the clock from the clock generation circuit 10 and the synchronization auxiliary signal from the synchronization pattern detector 8 and outputs them to the switch 3 and the clock generation circuit 10.

The position control circuit 11 generates a tracking error signal based on the data (data in the servo area of the magnetic disk 1) from the reproducing amplifier 4 and controls the VCM 12 based on this tracking error signal.

Next, the operation will be described. When the power supply of the device is turned on, the switch 3 is first switched to the P side, and in the magnetic head 2, the data corresponding to the magnetization direction of the magnetic disk 1 is output to the reproducing amplifier 4 via the switch 3. The reproduction amplifier 4 amplifies the data from the magnetic head 2 via the switch 3 and outputs it to the synchronization pattern detector 8 and the clock generation circuit 10.

The synchronization pattern detector 8 is the reproduction amplifier 4
And the 15-bit unique standard pattern (100110101111000) or index standard pattern (101011001000111) are ANDed in bit units to match the 15-bit unique standard pattern or index standard pattern with, for example, 14 bits or more. , A 15-bit bit string in the data string from the reproduction amplifier 4 is detected as a unique pattern or an index pattern.

As described above, the synchronization pattern detector 8 can detect the unique pattern or the index pattern from the data string from the reproduction amplifier 4 at a predetermined substantially constant timing, that is, in the initial stage. When synchronized, a synchronization auxiliary signal is generated at the timing of detecting the unique pattern or the index pattern, and the timing generation circuit 9 and the position control circuit 1 are generated.
Output to 1.

The timing generation circuit 9 outputs the synchronization auxiliary signal from the synchronization pattern detector 8 at the timing
A clock gate signal is output to the clock generation circuit 10. The clock generation circuit 10 separates the component corresponding to the clock pattern (FIG. 2) from the signal output from the reproduction amplifier 4 based on the timing when the clock gate signal is output from the timing generation circuit 9, and synchronizes with this. To generate a clock.

When the synchronization is established as described above, a window is opened in the synchronization pattern detector 8 at the timing at which the synchronization auxiliary signal is generated by itself, and an index pattern or a unique pattern from the reproduction amplifier 4 is created. The corresponding signal is received. Then, in the synchronization pattern detector 8, the 15-bit unique standard pattern or index standard pattern, for example, 13
A 15-bit bit string in the data string from the reproduction amplifier 4 that matches more than one bit is detected as a unique pattern or an index pattern.

After that, the synchronization pattern detector 8 outputs a phase synchronization auxiliary signal to the position control circuit 11 at the timing of detecting an index pattern formed only on one track of the magnetic disk 1. In the position control circuit 11, the initialization of the phase is performed at the timing when the synchronization pattern detector 8 outputs the phase synchronization auxiliary signal (the position of the phase 0 of the magnetic disk 1 is recognized).

Here, from the autocorrelation of the M series 101011001000111 as the index pattern shown in FIG. 6, this 15-bit index pattern and a 15-bit bit string deviated from the position on the magnetic disk 1 where it was recorded are shown. The number of bits that match with each other is 8 at most.

Furthermore, from the autocorrelation of the M sequence 100110101111000 as the unique pattern shown in FIG. 7, this 15-bit unique pattern and the 15-bit bit string deviated from the position on the magnetic disk 1 where it was recorded are obtained. The number of matching bits is 9 at most.

Also, M series 101011001000111 as the index pattern and M series 10011010111 as the unique pattern shown in FIG.
From the cross-correlation of 1000, the number of bits in which the index pattern and the unique pattern match the other pattern is at most 10 bits.

As a result, a 15-bit data string and 1
As a result of ANDing with the 5-bit unique standard pattern or the index standard pattern, if 11 bits or more match, the 15-bit data string is a unique pattern or an index pattern.

Therefore, even if the bit error (detection error) of 2 bits is taken into consideration, the 15-bit data string in the data string from the reproduction amplifier 4 and the unique standard pattern or the index standard pattern are If 13 bits or more match each other, the 15-bit data string can be regarded as a unique pattern or an index pattern.

In this case, if it is permitted that the probability that the index pattern and the unique pattern are erroneously detected by the other pattern is increased to some extent, 15 bits in the data string from the reproduction amplifier 4 will be used. If the data string of No. 1 and the unique standard pattern or the index standard pattern match 12 bits or more in bit units, the 15-bit data string can be regarded as the unique pattern or the index pattern.

As described above, in the synchronization pattern detector 8, after the synchronization is established, until the clock generation circuit 10 generates an accurate clock, it matches the unique standard pattern of 15 bits or the index standard pattern of 13 bits or more. The 15-bit bit string in the data string from the reproduction amplifier 4 is detected as a unique pattern or an index pattern.

Therefore, in the synchronization pattern detector 8, 1
Since it suffices to detect a pattern that matches at least 13 bits instead of all 15 bits with the 5-bit unique standard pattern or index standard pattern, the unique pattern or index pattern can be easily detected.

As a result, it is possible to prevent the unique pattern or the index pattern from being detected and the synchronization from being lost.

Since the operation of each block of the device is unstable at the time of starting the device, that is, at the time of initial synchronization, in the synchronizing pattern detector 8, as described above, the reproduction amplifier 4 is used.
If the 15-bit bit string in the data string from the data matches the 15-bit unique standard pattern or index standard pattern, which is one bit more than 13 bits, for example, 14 bits or more, the 15-bit bit string from the reproduction amplifier 4 is selected. It is designed to be detected as a unique pattern or an index pattern.

As described above, when the synchronization is roughly performed based on the detection timing of the unique pattern and the phase is further initialized based on the detection timing of the index pattern, the timing generation circuit 9 thereafter. The clock from the clock generation circuit 10 is counted, and at the timing when the clock pattern of the next segment (servo region) is generated, a clock gate signal is generated and output to the clock generation circuit 10. At the timing of this clock gate signal, the clock generation circuit 10 determines that the signal supplied from the reproduction amplifier 4 corresponds to the clock pattern, and repeats the operation of detecting this. In this way, the clock generation circuit 10 can generate a clock accurately synchronized with the clock pattern.

When the clock generation circuit 10 generates a clock accurately synchronized with the clock pattern,
That is, when accurate synchronization is established, when the operation mode of the apparatus is the recording mode, the timing generation circuit 9 counts the clocks from the clock generation circuit 10 and, for example, logic L, at the timing of the data area (FIG. 2). At the timing of the servo area (FIG. 2), for example, a switching signal of logic H is generated and output to the switch 3. The switch 3 is switched to the contact R side at the time of the logic L (at the timing of the data area) by the switching signal,
At the time of logic H (at the timing of the servo area), it is switched to the contact P side.

The position control circuit 11 detects the signal supplied from the reproduction amplifier 4 at the timing of the servo area.
A signal corresponding to the fine pattern (FIG. 2) is detected and a tracking error signal is generated from this. Then, the magnetic head 2 is controlled via the VCM 12 in response to this tracking error signal. As a result, the magnetic head 2
To accurately trace the track of the magnetic disk 1.

The recording data generating circuit 6 converts the input data into recording data at the timing of the data area and outputs it to the magnetic head 2 via the recording amplifier 7 and the contact R of the switch 3. As a result, the record data is recorded in the data area of the magnetic disk 1.

When the operation mode of the apparatus is the reproduction mode, the timing generation circuit 9 keeps the switch 3 at the contact P.
Switch to the side. As a result, the signal reproduced by the magnetic head 2 from the magnetic disk 1 is output to the data demodulation circuit 5 via the contact P of the switch 3 and the reproduction amplifier 4. In the data demodulation circuit 5, the signal (data in the data area) from the reproduction amplifier 4 is demodulated and output.

In this case, the position control circuit 11 operates similarly to the case where the operation mode of the apparatus is the recording mode.

The case where the recording / reproducing apparatus of the present invention is applied to a magnetic disk device has been described above.
In addition to the magnetic disk device, it can be applied to, for example, an optical disk device or a magneto-optical disk device.

In this embodiment, the M series is used for the index pattern and the unique pattern. However, not only the M series but also other PN series (Pseu) are used.
Do-Noise Sequence), or any sequence having strong autocorrelation with periodicity, such as a Legendre sequence (quadratic residue sequence) or a twin prime sequence, can be used.

Furthermore, in the present embodiment, the fourth-order M series is used for the index pattern and the unique pattern, but the present invention is not limited to this. However, M with a large order
When the sequence is used, the period of the M sequence becomes long due to the property (C1), that is, the sequence length of the M sequence becomes long. Therefore, in this case, the erroneous detection rate of the index pattern and the unique pattern is reduced, but it is difficult to detect. Therefore, the order of the M sequence is a value that balances this erroneous detection rate and ease of detection (for example, 4th order in this embodiment).

In this embodiment, the M series represented by the reciprocal polynomial of the equation (3) or (4) is used, but the polynomial representing the M series as the index pattern or the unique pattern is not always required. It does not have to be a reciprocal polynomial.

Further, on the magnetic disk 1, the clock pattern, the unique pattern, and the index pattern can be formed continuously in a radial pattern, or intermittently along the radius. You can

Further, each pattern of the servo area of the magnetic disk 1 can be physically formed by, for example, etching or the like, and it can be magnetically formed similarly to the case of recording data in the data area. You can

Furthermore, in this embodiment, the external synchronous disk device of the magnetic disk device has been described.
The M series can be used as a pattern for sector synchronization of the self-synchronous disk device.

Further, in the present embodiment, the magnetic disk 1 on which two synchronization patterns of a unique pattern and an index pattern are formed has been described, but the present invention is applicable to a magnetic disk on which one synchronization pattern is formed, for example. Can also be applied.

Further, in this embodiment, the M series is
Although it was used as a unique pattern as a pattern for establishing synchronization and an index pattern as a pattern for phase synchronization, it is not used as a pattern for establishing synchronization or phase synchronization but for other purposes such as a clock pattern. Can be used for.

Further, in this embodiment, in the synchronization pattern detection circuit 8, the reproduction amplifier 4 is used before and after the synchronization is established.
The unique pattern or the index pattern is changed by changing the number of bits (hereinafter, referred to as the detected bit number) in which the 15-bit bit string in the data string from No. 3 and the 15-bit unique standard pattern or the index standard pattern match in bit units. However, it is possible to detect the unique pattern or the index pattern without changing the number of detection bits before and after the synchronization is established.

Further, in the present embodiment, the number of detection bits when the index pattern and the unique pattern are detected by the sync pattern detection circuit 8 is set to the index pattern autocorrelation, the unique pattern autocorrelation, and the index pattern. Although the determination is made based on the cross-correlation of the unique pattern, it is possible to change the number of detection bits when detecting the index pattern or the unique pattern based on the autocorrelation of the index pattern or the unique pattern, respectively. it can.

Further, in this embodiment, P (1) to P (3) of the autocorrelation function P (s) in the fourth-order M series obtained based on the equation (3) or (4) are used. ) And P
The one having a smaller value of (-1) to P (-3) is used as the index pattern or the unique pattern of the magnetic disk 1, but the present invention is not limited to this.

That is, for example, in the index pattern,
P (1) to P (3) of the autocorrelation function P (s) in the fourth-order M series (or the M series obtained by cyclically permuting the M series) obtained based on the equation (3) And P (-
For example, 111101011001000 or the like can be used as an M sequence in which 1) to P (−3) are not small.

However, this M series 11110101100
The autocorrelation function P (s) of 1000 is as shown in FIG. 9, and when this M series is used as an index pattern, the pattern obtained by shifting the index pattern by, for example, +3 bits is a bit unit with the original index pattern. 10 bits match. Therefore, as compared with the case described with reference to FIG. 6, there is an increased possibility that a 15-bit bit string shifted by +3 bits from the position on the magnetic disk 1 where the index pattern is formed is erroneously detected as an index pattern. , As mentioned above,
An M sequence having smaller P (1) to P (3) and P (-1) to P (-3) of the autocorrelation function P (s) is
It is better to use it as an index pattern (or unique pattern) of the magnetic disk 1.

[0117]

As described above, according to the recording / reproducing apparatus of the present invention, the PN formed on the recording medium by the detecting means is used.
A synchronization pattern obtained by patternizing the sequence is detected from the output of the recording / reproducing means, and synchronization is performed based on the output of the detecting means. Therefore, so to speak, a pattern of a PN sequence having a strong autocorrelation is detected as a synchronization pattern, so that erroneous detection of the synchronization pattern is prevented,
It is possible to quickly establish the synchronization of the device and always operate the device normally.

Further, according to this recording / reproducing apparatus, since the synchronization pattern is a pattern of the M series of the PN series, this synchronization pattern can be easily generated.

Further, according to this recording / reproducing apparatus, the synchronization pattern has the first and second synchronization patterns.
Alternatively, since the second synchronization pattern is a pattern of different M series, it is possible to prevent the unique pattern and the index pattern from being erroneously detected as the other pattern.

Further, according to this recording / reproducing apparatus, the first
Since the synchronization pattern of is a synchronization establishment pattern for establishing synchronization, and the second synchronization pattern is a phase synchronization pattern for achieving phase synchronization, it is possible to quickly establish synchronization and to achieve phase synchronization. You can

Further, according to this recording / reproducing apparatus, the detecting means matches the same pattern as the first or second synchronization pattern in which the M sequence is patterned with the output from the recording / reproducing means, and the coincidence is achieved. When the number of detected bits is equal to or larger than a predetermined number of detected bits, a detection signal indicating that the first or second synchronization pattern has been detected from the output from the recording / reproducing means is output, and the first or second Since the predetermined number of detected bits is changed based on the autocorrelation of each of the M sequences forming the synchronization pattern,
The first and second synchronization patterns can be easily detected.

Further, according to this recording / reproducing apparatus, the detecting means matches the same pattern as the first or second synchronization pattern in which the M sequence is patterned with the output from the recording / reproducing means, and the coincidence is achieved. When the number of detected bits is greater than or equal to a predetermined number of detected bits, a detection signal indicating that the first or second synchronization pattern has been detected from the output from the recording / reproducing means is output, and before the synchronization is established. After that, the predetermined number of detection bits is changed, so that the predetermined number of detection bits can be made smaller after the synchronization is established, as compared with before the synchronization is established, and thus the unique pattern And the index pattern can be easily detected.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a magnetic disk device to which a recording / reproducing device of the present invention is applied.

FIG. 2 is a diagram showing a format of the magnetic disk 1 of FIG.

FIG. 3 is a block diagram showing a configuration example of a linear shift register circuit that generates an M sequence.

FIG. 4 is a block diagram showing a configuration example of a linear shift register circuit expressed by equation (4).

FIG. 5 is a diagram showing a unique pattern and an index pattern formed on the magnetic disk 1.

6 is a diagram showing an autocorrelation function of an index pattern formed on the magnetic disk 1. FIG.

7 is a diagram showing an autocorrelation function of a unique pattern formed on the magnetic disk 1. FIG.

FIG. 8 is a diagram showing a cross-correlation function between an index pattern and a unique pattern formed on the magnetic disk 1.

FIG. 9 is a diagram showing an autocorrelation function of M-sequence 111101011001000.

FIG. 10 is a diagram showing a format of a conventional magnetic disk 21.

FIG. 11 is a diagram showing a unique pattern and an index pattern formed on a conventional magnetic disk 21.

[Explanation of symbols]

 1 magnetic disk 1a substrate 1b magnetic layer 2 magnetic head 3 switch 4 reproducing amplifier 5 data demodulating circuit 6 recording data generating circuit 7 recording amplifier 8 synchronization pattern detector 9 timing generating circuit 10 clock generating circuit 11 position control circuit 12 VCM 21 magnetic Disk 21a Substrate 21b Magnetic layer

Claims (9)

[Claims] 1. A recording medium having a synchronization pattern formed by patterning a PN sequence, recording / reproducing means for recording or reproducing information on the recording medium, and the synchronization pattern from the output from the recording / reproducing means. A recording / reproducing apparatus comprising: a detecting unit for detecting and a synchronizing unit for synchronizing based on an output of the detecting unit. 2. The recording / reproducing apparatus according to claim 1, wherein the synchronization pattern is a pattern of an M series of the PN series. 3. The synchronization pattern includes first and second synchronization patterns, and the first or second synchronization pattern is a pattern of different M sequences. The recording / reproducing apparatus according to claim 2. 4. The first or second synchronization pattern comprises:
The recording / reproducing apparatus according to claim 3, wherein the recording / reproducing apparatus has the same sequence length. 5. The recording / reproducing apparatus according to claim 2, wherein the M-sequence is generated from a linear feedback shift register circuit expressed by a reciprocal irreducible polynomial. . 6. The first synchronization pattern is a synchronization establishment pattern for establishing synchronization, and the second synchronization pattern is a phase synchronization pattern for achieving phase synchronization. Item 3 or 4
The recording / reproducing device according to. 7. The detection means matches the same pattern as the first or second synchronization pattern obtained by patterning the M sequence with the output from the recording / reproducing means, and the number of coincident bits is predetermined. When the number of detection bits is equal to or more than the number of detection bits, a detection signal indicating that the first or second synchronization pattern is detected from the output from the recording / reproducing device is output, and the first or second synchronization pattern is output. 7. The recording / reproducing apparatus according to claim 3, wherein the predetermined number of detected bits is changed based on the autocorrelation of each of the M sequences constituting the. 8. The detection means matches the same pattern as the first or second synchronization pattern obtained by patterning the M sequence with the output from the recording / reproducing means, and the number of coincident bits is predetermined. When the number of detection bits is equal to or more than the number of detection bits, the detection signal indicating that the first or second synchronization pattern is detected from the output from the recording / reproducing means is output, and before and after synchronization is established. 7. The recording / reproducing apparatus according to claim 3, wherein the predetermined number of detection bits is changed. 9. The recording / reproducing apparatus according to claim 1, wherein the recording medium is a magnetic disk, and the recording / reproducing unit is a magnetic head.