JP3313928B2 - Data modulation method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data modulation method and apparatus for binary data, and more particularly to a method and apparatus for modulating a run length limited code used for recording on an optical disk.

[0002]

2. Description of the Related Art To transmit a digital data sequence, it is necessary to modulate the digital data sequence into a signal suitable for a transmission line (channel) such as a communication line or a recording device used for transmission. Various modulation methods have been proposed for optical discs, particularly for achieving high recording densities. FIG. 9 is a diagram showing a typical modulation method.
The input data to be written to the disc is once converted to code data by a code converter, and further converted to NRZI (Non-
The signal is converted into an NRZI signal by a Return to Zero-Inverse (Converter) converter and sent to an optical disk head.

FIG. 10 is a diagram showing an example of data to be modulated. FIG. 10 shows 4-bit input data, 8-bit code data obtained by converting the input data, and a signal waveform after NRZI conversion. . The waveform of the NRZI signal is
Due to the frequency characteristics of the channel and the tracking control of the disk head, the inversion interval (HI or LO of the signal waveform)
Is limited to a certain range, DC
It is required that the component (difference between the durations of HI and LO of the signal waveform) be small. Therefore, when converting input data into code data, the inversion interval of the obtained code data must always be within a certain range. In this way, the code data is called a run length limited code because the inversion interval is limited.

[0004] As a scale representing the attribute of the run length limited code,
There are (d, k) restrictions. The (d, k) constraint means that the inversion interval in the code data, that is, the number of consecutive 0s between 1 is d or more (generally called a d constraint) and k or less (generally called a k constraint). It means that the restriction has to be satisfied. The (d, k) constraint needs to be satisfied not only in one piece of code data but also in a portion over two or more consecutive code data.

In order to obtain a code data string satisfying such restrictions, the conventional code converter performs data modulation according to the procedure of a flowchart shown in FIG. That is, first, given individual input data is converted into corresponding code data based on a predetermined conversion table (step S1101). Subsequently, if the (d, k) constraint is not satisfied for a portion straddling adjacent code data, Tmin control and Tmax control are performed (step S1).
102). Here, the Tmin control refers to rewriting a part of the code data so as to satisfy the d constraint.
The max control refers to rewriting a part of the code data so as to satisfy the k constraint.

Finally, in order to perform control for reducing the DC component of the NRZI signal (hereinafter referred to as DC control), a part of the code data is rewritten (step S1103).
The DC component of the NRZI signal is the difference between the total number of 1s and the total number of 0s in a certain section (hereinafter referred to as DSV
m Value). ). For optical discs,
In order to stably determine 1/0 of the read signal, it is necessary that the DC component is small.

The above procedure will be described using specific input data. As an example, consider a case where 4-bit input data is converted into 8-bit code data satisfying the (2, 9) constraint. Further, the table shown in FIG. 12 is adopted as the predetermined conversion table used in step S1101. The input data in the table shown in FIG. 12 is represented by a binary number and a hexadecimal number.

[0008] The 16 code data shown in FIG. 12 not only satisfies the (2, 9) constraint, but also easily satisfies the (2, 9) constraint over a portion straddling adjacent code data. It was chosen in consideration of That is, the 16 pieces of code data shown in FIG. 12 are code data starting from 1 among 28 pieces of code data which are all combinations of 8 bits satisfying the following (2, 9) constraints; Code data with a large number of consecutive 0's $ 0000
0000 00000001 01000000｝ has been removed. ｛00000000 00000001 00000010 00000100 00001000 000
01001 00010000 00010001 00010010 00100000 00100001
00100010 00100100 01000000 01000001 01000010 0100
0100 01001000 01001001 10000000 10000001 10000010
10000100 10001000 10001001 10010000 10010001 10010
010｝ Now, as input data, 5, D, 7, 0 (Hex display)
Are given in sequence.

The input data is converted into four code data strings {00010001 01000100 00100000 00000010} based on the conversion table of FIG. 12 (step S11).
01). Here, {101} in a portion straddling the first code data and the second code data violates the d constraint of the (2, 9) constraint. Therefore, it is necessary to perform Tmin control.
Now, Tmin control is defined as follows. [Tmin control]: {XXXXX001 0100XXXX}> {XXXXX000 1000XXXX} That is, when the code data string becomes {XXXXX001 0100XXXX}, it is rewritten to {XXXXX000 1000XXXX}.

Accordingly, the above-mentioned code data string becomes a code data string of {00010000 10000100 00100000 00000010} by the Tmin control (step S1102). By the way, this code data string is composed of the first code data and the second code data.
Although a part of the code data has been rewritten, the second code data starts with 1 and is not present in the conversion table of FIG. Therefore, it is understood that this code data string can be returned to the original code data string, that is, demodulation is possible.

Next, focusing on a portion of the code data sequence obtained by the above-described Tmin control that spans the third code data and the fourth code data, {100000 0000001} becomes
(2, 9) Violates the k constraint of the constraint. Therefore, it is necessary to perform Tmax control subsequently. Now, Tmax control is defined as follows. [Tmax control]: ｛00100000 00000010｝> ｛00100100 10010010｝ or ｛00100000 10010010 ｛｛00100000 00000100 ｛> ｛00100100 10000100｝ ｛00010000 00000010｝> ｛00010000 10010010｝ That is, the code data string becomes ｛00100000 00000010｝ In this case, ｛00100100 10010010｝ or ｛00100000 10
On 010010, the code data string is {00100000 00000100}
Becomes {00100100 10000100} when it becomes, and 000 when the code data string becomes {00010000 00000010}
Rewrite to 10000 10010010｝.

Therefore, the above-mentioned code data string can be converted into {00010000 10000100 00100100 10010010} or {00010 by Tmax control.
A code data string of 000 10000100 00100000 10010010｝ is obtained (step S1102). In these code data strings, the fourth code data is 1
It can be seen that demodulation is possible because the code data starts with.

When the two code data strings obtained as a result of the above Tmax control are subjected to NRZI conversion, they are {00011111 00000111 11000111 00011110} and {0001111, respectively.
1 00000111 11000000 11100011｝ Therefore, by choosing one, D
It can be seen that C control is possible (procedure 3).

As described above, the conventional code converter uniquely converts input data into code data on the basis of a conversion table created in advance, and then converts the input data into a defective portion in a portion extending over a plurality of code data. Was to change.

[0015]

Generally, in selecting code data, it is necessary to utilize as much code data as possible from all selectable code data, that is, the 28 types of code data shown above. Obviously, this is the preferred data conversion scheme. In data conversion on optical discs that require high recording density,
In particular, effective use of code data is desired. Also, if there are many types of code data that can be used, more information can be included in the code data, so that more flexible and diverse control is possible. For example, finer DC control becomes possible, and it is possible to cope with an improvement in the recording density of a disk.

However, in the conventional method, one input data is converted into one code data by using a conversion table. When the input data is converted into the code data, another input data is selected as the code data. Despite there is
The conversion does not take those options into account. That is,
Encoding is performed using only 16 types of code data among the 28 types of code data shown above, and thereafter the code data is changed as necessary. Therefore, when converting the input data into the code data, the scope for selecting the corresponding code data is narrowed.

Specifically, for example, consider a case where code data {00000001} not used in the conversion table shown in FIG. 12 is used. When code data {00000001} is sandwiched between specific code data, for example, {XXXX0100 000
[00001] If 0100XXXX}, the portion straddling the second code data and the third code data violates the (2, 9) constraint, so that Tmin control is performed. As a result ｛XXXX00100 0
000000 1000XXXX}, but since this code data string has a portion where ten 0s are continuous, it still violates the (2, 9) constraint. Therefore, this code data {00000001} cannot be used.

Similarly, for {01000000}, {XXXX
In the case of X001 01000000 000100XX}, the result of the Tmin control is {XXXXX000 10000000 000100XX}, which cannot be used because there are 10 consecutive zeros. Furthermore, for ｛00000000｝, ｛XXXXX010 00000000
When the value is 001000XX｝, the Tmin control and the Tmax control cannot be performed, and there is a portion where 11 0s are continuous.

As described above, in the conventional data modulation method,
Since the selectable code data is limited, flexible control is hindered, and code data having a larger number of bits has to be adopted, thereby preventing a high recording density of the disk. Therefore, the present invention has been made in view of such a problem, and a first object of the present invention is to provide a data modulation method and a data modulation method capable of converting into code data containing a wealth of information.

A second object of the present invention is to provide a data modulation method and an apparatus for converting data into an efficient run length limited code. Further, a third object of the present invention is to provide a data modulation method and apparatus for converting data into code data containing information for controlling a DC component of output code data.

[0021]

In order to achieve the above object, a data modulation method according to the present invention converts an input code consisting of a predetermined number of bits which are continuously provided into an output code consisting of more than the predetermined number of bits. a data modulation method for outputting in series with a first step of selecting a set of Do that output symbols as candidates for each input code based on a predetermined conversion table, and input code to be modulated the input Between each candidate set selected by the first step for the input code adjacent to the code and the adjacent output code
And a second step of determining output codes each satisfying a predetermined constraint.

Here, the output code is a run length limited code in which the number of consecutive two values is limited to a predetermined range.
An output code that satisfies the above-mentioned restriction even in a portion straddling one output code is selected from the set.

Here, the second step further minimizes the difference between the total number of 1 bits and the total number of 0 bits in a code string obtained by subjecting a predetermined number of consecutive output codes to NRZI conversion. Such an output code is selected from the set. Further, the data modulation apparatus of the present invention is a data modulation apparatus that converts an input code consisting of a predetermined number of bits that are continuously provided to an output code consisting of more bits than the predetermined number, and outputs the output code in series. an apparatus, and a candidate set determining means for determining an index indicating the set of candidate Do that output codes to one input codes given input adjacent the input code and the input code to be modulated An output code adjacent to the code from each index determined by the candidate set determination means.
And selecting means for selecting an optimal one output code that satisfies a predetermined constraint between the output code and the output code selected by the selecting means. I do.

Here, the output code is a run length limited code in which the number of consecutive two values is limited to a predetermined range, and the selecting means outputs the output code to two consecutive output codes. Judging means for judging whether or not the limitation is satisfied in the straddling portion, and one output code which satisfies the limitation is determined based on the judgment result by the judging means and the index determined by the candidate set determining means. Determining means for selecting from the set.

Here, the selection means further includes a DC component calculation for calculating a difference between a total number of 1 bits and a total number of 0 bits in a code string obtained by subjecting a predetermined number of continuous output codes to NRZI conversion. Means for determining one output code that minimizes the difference between the total number from the set based on a result of the DC component calculation means.

[0026]

SUMMARY OF] According to the data modulation method及beauty data modulation apparatus of the present invention configured as described above, when the input code is applied continuously, based on a predetermined conversion table, for each input code set of output codes that Do the candidate Te is determined. An adjacent output code from each of the sets obtained for an input code to be modulated and an input code adjacent to the input code.
Output code which satisfies a predetermined constraint it between No.
Is determined. The determined output code is output in series.

Further, according to the data modulation method及beauty data modulation apparatus of the present invention, the output code is run length limited code number of either binary value is continuous is limited to a predetermined range Limited to only. Further, the finally obtained output code is selected in such a manner as to satisfy this limitation even in a portion straddling two consecutive output codes, and is output in series. Therefore, in any part of the output code that is continuously output, the number of consecutive two values falls within a predetermined range.

Further, according to the data modulation method及beauty data modulation apparatus of the present invention, furthermore, the total number of 1 bits in the output code of a predetermined number of consecutive converted NRZI code sequence and zero bits An output code that reduces the difference in the total number is selected. Therefore, the output code that is continuously output is not only in any part, the number of consecutive values of any of the two values is within a predetermined range,
The output code is controlled so that the DC component of the NRZI-converted signal waveform is reduced.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings. Code modulation under the same conditions as those described in the related art, that is, under the (2, 9) constraint, 4-bit input data is converted to 8-bit code data,
Further, a case of a data modulation device that performs NRZI conversion will be described. (Configuration of Apparatus) FIG. 1 is a block diagram showing the configuration of a data modulation apparatus according to the present embodiment.

The present apparatus includes a candidate set index determining unit 1
01, the symbol number determination unit 102, the post-processing circuit 106,
107, NRZI converter 108, FIFO memory 10
9, the DC control unit 110, and other registers and logic circuits. Candidate set index determination unit 101
Is composed of a ROM or the like that stores the candidate set index table shown in FIG. 2 and outputs a corresponding 6-bit candidate set index when 4-bit input data is input.

The candidate set index table shown in FIG. 2 shows input data, a candidate set index for the input data, and code data belonging to the candidate set. Note that the column of code data belonging to the candidate set index in this table is provided for reference.
Here, the candidate set index indicates a set of a plurality of code data. For example, like AC
Two alphabets are connected by '-' to form a set of indexes. The set indicated by the candidate set index is created such that the code data to be finally obtained always exists in the set.

For the code data belonging to the candidate set, symbol numbers are used for convenience of expression. Here, the symbol number is defined as shown in the symbol number table shown in FIG. 3 corresponding to the front or rear 4 bits of the 8-bit code data. For example,
Symbol number sequence 4-2 is equal to code data {10000010}.

As for the output candidate set index, a candidate set index corresponding to the latest three pieces of input data is input to input terminals S1 to S5 of the symbol number determination unit 102 by a register Reg for delay operation. The symbol number determination unit 102 includes a ROM or the like in which the target index table shown in FIG. 4 and the symbol number conversion table shown in FIG. 5 are stored, and based on the input 15-bit candidate set index sequence, A symbol number sequence and a decision flag are output.

More specifically, if the index set of interest shown in FIG. 4 exists for the input candidate set index sets S1 to S5, the corresponding a candidate a1a2a
The symbol number sequence of 3a4 and b candidate b1b2b3b4 is output, and for the candidate set index excluding the index sequence of interest, the corresponding symbol number is provisionally determined according to the symbol number conversion table shown in FIG. Each symbol number is a numerical value from 0 to 5 as shown in the symbol number table of FIG.

In the target index table, '='
It means a connection part of different input data. When a plurality of candidate set indices are arranged without interposing "-", it means any one of the candidate set indices. For example, the focused index sequence BF =
CA = D means that the tail of the candidate set index obtained immediately before the candidate set index CA is B or F, that is, B
= CA = D or F = CA = D represents a candidate set index sequence.

As in the case of the symbol number sequence, the determination flags f3 and f4 corresponding to the input candidate set index sequences S1 to S5 are output from the symbol number determination unit 102. The decision flag is provided in the symbol number sequence a
Since 3a4 (same for b3b4) overlaps a1a2 (b1b2) that is processed next in time, a3a4 (b3
b4) may be rewritten by a1a2 (b1b2) in the next process, but this is to avoid this. The switches SW1 and SW2 shown in FIG. 1 have this role, and FIG. 1 shows a state where f3 = f4 = 0. A3a4 (b3
In the case of b4), the same symbol number is output in the next process and is not rewritten. In addition, a1a2
The determination flags f1 and f2 corresponding to (b1b2) are a1
Since a2 (b1b2) is not rewritten at the next timing, it is not output from the symbol number determination unit 102.

The symbol number sequence of the candidate a output from the symbol number determination unit 102 is sent to the post-processing circuit 106, and the symbol number sequence of the candidate b is sent to the post-processing circuit 107. still,
The post-processing circuit 106 and the post-processing circuit 107 have the same configuration. The multiplexer 103 includes the symbol number determination unit 1
02 and the parallel symbol number sequence a1a2 (b1b
2) is converted to a serial symbol number sequence and sent to the code data determination unit 104.

The code data determining unit 104 that has received the symbol number converts the code data into corresponding code data based on the symbol number table shown in FIG. The converted code data is bit-serialized by P / S 105 and
It is sent to the RZI conversion unit 108 and the exclusive OR EX-OR. Thus, the candidate set index determining unit 10
For one 4-bit input data input to 1, a
One piece of 8-bit code data called a candidate and one piece of 8-bit code data called a b candidate are obtained from the post-processing circuits 106 and 107, respectively.

The code data of the a candidate and the b candidate are compared by exclusive OR, and the result (hereinafter, referred to as DSV control bit) is sent to the DC control unit 110. DC
Control unit 110 outputs N, which is the output of NRZI conversion unit 108.
The DSV of the RZI signal is calculated. DC control unit 110
If the code data can be selected, that is, if the pattern of the code data of the candidate a and the pattern of the code data of the b candidate are different, N
The RZI signal is stored in the FIFO memory 109,
The exclusive OR EX of the FIFO memory 109 and the output stage is output so that the NRZI signal with the smaller DSV is output.
-OR is controlled. As a result, an NRZI signal having a small DC component is obtained.

Specifically, the DC control section 110 operates as follows. First, by detecting the DSV control bit,
DSV1 + DSV2 and DSV1-DSV2 are evaluated to detect the one having the smaller absolute value, and the FIFO is adjusted so as to match this.
The output of the memory is inverted or non-inverted by EX-OR and output. This is because the value of DSV2, which is a temporary DSV calculation value, is inverted and given by 1/0 of the DSV control bit, and the NRZI signal may be inverted or non-inverted.

Next, DSV1 + DSV2 and DSV1-D
The smaller absolute value of SV2 is referred to as DSV1. at the same time,
DSV2 is initialized (DSV2 = 0), and DSV2 up to the next DSV control bit is calculated. The above operation is repeated. (Modulation Procedure) Next, the operation of the data modulation device configured as described above will be described based on the flowchart shown in FIG. 6 and specific input data.

Now, input data strings 5, D, 7, 0,.
A description will be given of a procedure in which data is converted when 8, 7, E,. The conversion results in each procedure described below are summarized in a table shown in FIG. The candidate set indices and symbol numbers described in this table are arranged so that before and after the conversion corresponds to the vertical direction of the table.

First, when the input data string is given to the candidate set index determining unit 101 (step S60)
1), based on the candidate set index table of FIG. 2, a candidate set index sequence = BB = DD = CA = AC
= And = CB = CA = DE = are obtained (step S602). Next, these candidate set index strings are converted into symbol number strings by the symbol number determination unit 102 (step S603).

More specifically, among the candidate set index strings, the noted index strings registered in the noted index table shown in FIG. 4 are B = D, C−A =
AC and B = CA = D. The symbol number sequence corresponding to these target indexes is 0 = 4, 2-
3 = 5-2 or 2-0 = 5-2 and B = 2-0 = D
Or, B = 0-0 = D. Further, the complete symbol number sequence output based on the symbol number conversion table shown in FIG. 5 is: = 1-0 = 4-3 = 2-3 = 5-2 = or = 1-0 = 4- 3 = 2-0 = 5-2 = and = 2-
1 = 2-0 = 3-4 = or = 2-1 = 0-0 = 0 = 3-
4 =.

These symbol number strings are stored in a multiplexer 103, a code data determination unit 104, and a P / S 105.
(Step S6)
04). Specifically, the final code data sequence obtained based on the symbol number table shown in FIG. 3 is {00010000 10000100 00100100 10010010} or {000
10000 10000100 00100000 10010010｝ and ｛00100001 00100000 01001000｝ or ｛00100001
00000000 01001000｝.

The above code data string satisfies the (2, 9) constraint in any part. Also,
For the first half of the above code data string, that is, the code data string whose input data corresponds to 5, D, 7, 0,
It can be seen that the result is consistent with the result obtained in the conversion example according to the conventional technique of this specification. The obtained code data string is NR
The signal is converted into an NRZI signal by the ZI conversion unit 108 (step S605). Then, the DC control unit 110
It is determined whether DC control is possible (step S60)
6).

In this example, the input data strings 5, D, 7, 0
A different for each of the input data 8, 7, and E
Since the code data strings of the candidate and the b candidate are obtained, D
When selecting a code data string for input data strings 5, D, 7, and 0, C control section 110 obtains DSVs of NRZI signals until input data strings 8, 7, and E are next provided. Then, the NRZI signal corresponding to the code data having a smaller DSV is selected (step S607), and is controlled so as to be output (step S608).

According to the above procedure, the present apparatus obtains an NRZI signal that satisfies the constraint (2, 9) and suppresses the DC component from a given input data sequence. One of the features of the code modulation in this embodiment is that although the finally obtained code data is almost the same as the code data obtained by the conventional code modulation, the modulation process is completely different. That is, the code modulation according to the present embodiment includes a first step of generating a candidate set index sequence,
A second step of narrowing down to one optimal code data by detecting a target index sequence from the candidate set index sequence, and Tmin
The difference from the conventional method is that a series of controls such as control and Tmax control are performed in the same procedure.

Another feature of the code modulation according to the present embodiment is that, in the process of narrowing down to code data, a plurality of candidates are left to provide a room for selection. Can be done at the same time. That is, by using code symbols that cannot be used in the conventional method, data modulation is performed more effectively than in the conventional method.

Here, the “code symbols that cannot be used in the conventional method” are {00000000}, {00000001} and {01000000} described in the conventional technique of this specification. In the present embodiment, two code symbols of {00000000} and {00000001} among these three code symbols are used as selectable code symbols.

More specifically, the target index sequence BF = CA = D and BC registered in the target index table
Symbol number sequence 15 corresponding to DF = BB = ABC
0-0 = 3 and 1235 = 0-1 = 012 correspond.
That is, 0-0 and 0- in the two symbol number strings
1 is code data {00000000} and {0000000 respectively
It corresponds to 1｝.

As described above, it can be seen that two code symbols that cannot be used in the conventional method are adopted as conversion targets in the code modulation of the present embodiment. Note that the code symbol $ 01 that could not be used in the conventional method
000000｝ is passively used in this embodiment. That is, for example, when two pieces of input data are B and C, the obtained candidate set index sequence is shown in FIG. Is DB = DC from the candidate set index table shown in (1), and the symbol number sequence obtained from the focused index table and the symbol number conversion table is 3-0 = 4-2. The code data obtained is $ 0100
0000 {10000010}. Therefore, it can be seen that the code data obtained by converting the input data B corresponds to {01000000}, and is used passively.

As described above, the code modulation of the present embodiment uses code symbols that cannot be used in the conventional method for the purpose of DC control, so that only code conversion that satisfies the (2, 9) constraint is performed. Instead, code data that satisfies other constraints is generated at the same time, and code data within the allowable range is used to the full. (Demodulation procedure) Next, the NR obtained by the above modulation procedure
A procedure for demodulating a ZI signal, that is, a procedure for restoring an NRZI signal to input data before being modulated will be described.

The demodulation procedure is basically an inverse conversion using the same table as the above-mentioned modulation procedure. In the first place, in the modulation procedure of this data modulation, even if a plurality of selectable code data are output for one input data, it is impossible to output the same code data for a plurality of input data. It is clear that demodulation is possible because there is no demodulation. Specifically, demodulation is performed in the following procedure. (1) By performing inverse NRZI conversion on the NRZI signal,
Get the code data string. (2) The code data sequence is inversely converted into the symbol number sequence based on the symbol number table shown in FIG. (3) The symbol number sequence is converted into a candidate set index sequence according to the demodulation conversion table shown in FIG. Note that symbol numbers not shown in the demodulation conversion table of FIG. 8 are inversely converted to candidate set indexes according to the symbol number conversion table of FIG. (4) The obtained 6-bit candidate set index is inversely converted into 4-bit input data based on the candidate set index table shown in FIG.

As described above, the data modulation device according to the present invention has been described based on the embodiments, but it is needless to say that the present invention is not limited to these embodiments. That is, (1) In the present embodiment, 4-bit input data is converted into 8-bit code data, but the present invention is not limited to such a data length. For example, input data of 8 bits may be modulated to code data of 15 bits. (2) In this embodiment, the run length limited code that satisfies the (2, 9) constraint is output, but the present invention is not limited to this value. (3) In the present embodiment, code data that cannot be used in the conventional method is used for the purpose of DC control, thereby maximally utilizing the allowable range of code data. However, the present invention is not limited to such a purpose. Not something. For example, it can be used for the purpose of increasing the total number of 1s appearing in the code data. By performing such NRZI conversion on the code data, an NRZI signal having a smaller average inversion interval can be obtained, and a preferable waveform is obtained for a PLL circuit for reading data.

[0056]

As apparent from the foregoing description, according to the data modulation method及beauty data modulation apparatus of the present invention <br/>, firstly,
Each input code set of output symbols that Do candidates against is determined and then, from the set of each obtained for adjacent input code, satisfy the predetermined constraints between adjacent output code
The output codes to be added are respectively determined. The set can include many types of codes that can be used in advance. Therefore, the same input data can be modulated into more types of output codes than in the past, so that the output codes can be effectively used. As a result, there is an effect that abundant information can be included in the output code, not just code conversion.

[0057] Further, according to the data modulation method及beauty data modulation apparatus of the present invention, (d, k) output code that satisfies the constraints are determined in a single step. Accordingly, the input data can be modulated into the run length limited code by a smaller number of procedures than in the prior art, so that the data modulation can be speeded up. Further, according to the data modulation method及beauty data modulation apparatus of the present invention, reference numeral selectable output is used to suppress the DC component of the NRZI signal. Accordingly, the DC component of the signal obtained by subjecting the obtained output code to NRZI conversion is smaller than in the related art, so that there is an effect that a reading error at the time of reading the NRZI signal can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a data modulation device according to an embodiment.

FIG. 2 is a candidate set index table according to the embodiment.

FIG. 3 is a symbol number table according to the embodiment.

FIG. 4 is an index table of interest according to the embodiment.

FIG. 5 is a symbol number conversion table according to the embodiment.

FIG. 6 is a flowchart showing an operation procedure of the data modulation device according to the embodiment.

FIG. 7 is a table showing a conversion result of an input data string in the embodiment.

FIG. 8 is a demodulation conversion table according to the embodiment.

FIG. 9 is a block diagram showing a configuration of a conventional data modulation device.

FIG. 10 is a diagram showing an example of data in a conventional data modulation device.

FIG. 11 is a flowchart showing an operation procedure of a conventional data modulation device.

FIG. 12 is a conversion table from input data to code data according to a conventional data modulation device.

[Explanation of symbols]

 Reference Signs List 101 candidate set index determination unit 102 symbol number determination unit 103 multiplexer 104 code data determination unit 105 P / S 106 post-processing circuit 107 post-processing circuit 108 NRZI conversion unit 109 FIFO memory 110 DC control unit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Kojima 70 Yanagimachi, Yuki-ku, Kawasaki, Kanagawa Prefecture Inside the Toshiba Yanagimachi Plant (72) Inventor Koichi Hirayama 70 Yanagimachi, Yuki-ku, Kawasaki, Kanagawa Prefecture Co., Ltd. In the Toshiba Yanagimachi Plant (56) References JP-A-62-16619 (JP, A) JP-A-63-20920 (JP, A) JP-A-5-284035 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H03M 7/14 G11B 20/14 341

Claims (8)

(57) [Claims] 1. A data modulation method for converting an input code consisting of a predetermined number of bits continuously given to an output code consisting of more than the predetermined number of bits and outputting the converted data in series, based on a predetermined conversion table. that Do the candidates for each input code Te
A first step of selecting the set of output code, the output code adjacent from the group consisting input code to be modulated and the respective candidate selected by the first step with respect to input code adjacent to the input code And a second step of respectively determining output codes that satisfy a predetermined constraint between the data modulation method and the data modulation method. 2. The output code is a run-length limited code in which the number of consecutive two values is limited to a predetermined range, and the second step includes two consecutive output codes. 2. The data modulation method according to claim 1, wherein an output code that satisfies the above restriction is selected from the set even in a portion straddling. 3. The second step further comprises: minimizing a difference between a total number of 1 bits and a total number of 0 bits in a code string obtained by subjecting a predetermined number of continuous output codes to NRZI conversion. 3. The data modulation method according to claim 2, wherein a proper output code is selected from the set. 4. A data modulator for converting an input code consisting of a predetermined number of bits continuously given to an output code consisting of more than the predetermined number of bits and outputting the output code in series, wherein one given input is provided. a candidate set determining means for determining an index indicating a set of output code that Do candidates to the code, determined by the candidate set determining unit for the input code which is adjacent to the input code and the input code to be modulated Between each output index and the adjacent output code
Selection means in selecting the predetermined constraints satisfying one optimum output code as a feature in that it comprises a means for outputting a signal in bit series by the selected converting the output code of a predetermined by the selection means Data modulation device. 5. The output code is a run-length limited code in which the number of consecutive binary values is limited to a predetermined range, and the selecting unit extends over two consecutive output codes. Determining means for determining whether or not the part satisfies the restriction; and, based on the determination result by the determining means and the index determined by the candidate set determining means, one output code satisfying the restriction is 5. The data modulation device according to claim 4, further comprising: a determination unit that selects from a set. 6. A DC component calculating means for calculating a difference between a total number of 1 bits and a total number of 0 bits in a code string obtained by subjecting a predetermined number of consecutive output codes to NRZI conversion. 6. The method according to claim 5, wherein the determining unit further selects one output code that minimizes the difference between the total number from the set based on a result of the DC component calculating unit. The data modulation device according to claim 1. 7. Input data consisting of a predetermined number of bits
Consists of more bits than the specified number
Data whose code length is restricted to a specified range.
Data modulation device, wherein an index defining an index corresponding to each input data is provided.
Means for storing an index conversion table, and a symbol for defining a symbol number corresponding to each index.
Means for storing the file number conversion table, and the run length corresponding to each symbol number is limited to a predetermined range.
Means for storing a code conversion table that defines the code being used, and an index string that is stored in the symbol number conversion table and the code.
When converted to a code string by the conversion table,
Attention that the part that does not satisfy the run length limit
Regarding the index sequence, the part straddling the code
The code conversion table converts the code string to satisfy the length restriction.
Corresponding constant meta attention Independiente to a symbol number column, such as
Means for storing an index table, and converting an input data string which is continuously input into the index table.
First conversion method for converting to an index column based on a conversion table
In the column and the converted index sequence, the index of interest is added.
If the index table registered in the
Is the corresponding symbol based on the index table of interest.
If the number is not included, the symbol
Convert to the corresponding symbol number string based on the number conversion table
Second converting means and the code conversion of the symbol number sequence.
And third conversion means for converting into a code sequence based on the table.
A data modulator characterized by the above. 8. The data modulation device according to claim 7, wherein
hand, The noted index table corresponds to the noted index.
A plurality of corresponding symbol number strings, The second conversion means is configured to convert the converted index sequence
In the target index registered in the target index table,
If the index column is included, the index of interest
Is converted into a corresponding plurality of symbol number strings based on The third conversion means precedes the plurality of symbol number strings.
Based on the code conversion table, convert to a plurality of code strings, Each of the code strings is converted into a code string obtained by NRZI conversion.
Difference between the total number of 1 bits and the total number of 0 bits
Is calculated, and one symbol for minimizing the difference between the total number is calculated.
A data modulation device for selecting a signal sequence.