Coded data generation or conversion – Digital code to digital code converters – To or from run length limited codes
Reexamination Certificate
2001-12-03
2003-03-11
Young, Brian (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
To or from run length limited codes
C341S051000
Reexamination Certificate
active
06531968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to modulation of digital data, and more particularly, to a digital data modulating method and apparatus for quickly and accurately determining a code word to be modulated at a boundary between data blocks by using a constraint (d, k) of a run length limited (RLL) code, and a medium for recording a modulated data generated by using the same.
2. Description of the Background Art
In general, in methods for modulating data and recording it in a recording medium, if a signal detected from a recording medium is a binary ‘0’, a non-return-to-zero inverted (NRZI) code indicates that there is no change in a magnetic flux of the recording medium, while if the a signal detected from the recording medium is a binary ‘1’, the NRZI code indicates that the direction of a magnetic flux recorded in the recording medium is transited to the opposite direction, whereby data is recorded onto the recording medium and a recorded signal is detected or reproduced.
The recently used RLL code is an extended code of the NRZI code concept, which converts a 8 bit (1 byte) data to a 16 bit special code (code word). Accordingly, the data recording efficiency is improved as the code word is more densely stored in the recording medium.
For example, since 8 bits entail 256 types of bit combinations, and 16 bits entail 65536 types of bit combinations, the RLL code is generated by converting a 256-bit combination number generated by 8 bits into 256 numbers among the 65536-bit combination number generated by the 16 bits. At this time, the converted data should satisfy the following constraints.
A first constraint is that there should exist a bit having a value of at least one ‘0’ bit among bits having a value of successive ‘1’s.
For example, one data bit is thrice the data recording density stored without any special constraint, and thus, the data is recorded in the recording medium at a high recording density.
In this respect, the first constraint is that even though the data is recorded in the recording medium at a high recording density, it is to be at a distance which enables a magnetic flux polarity of the data bit recorded in the recording medium to be identified.
That is, the first constraint is that the bits having the value of ‘0’ are consecutively recorded in the recording medium, and when the recorded data is reproduced, no interference occurs among the symbols.
A second constraint is to restrict the number of ‘0’s between the ‘1’ bits. The second constraint restores a clock signal from reproduced data by locking a phase locking circuit to the transitions when the data being reproduced are transited.
The RLL code is expressed as (d, k) code, wherein ‘d’ indicates the minimum number of bits having a value of ‘0’ that is inserted between bits having a value of ‘1’, and ‘k’ indicates the maximum number of bits having a value of ‘0’ that is inserted between the bits having a value of ‘1’.
For example, (1, 7) code signifies a code which satisfies a constraint in that bits having a value of at least one ‘0’ should exist among the bits having a recorded value of ‘1’, and bits having a value of a maximum of seven consecutive ‘1’s should exist among the bits having a recorded value of ‘1’.
At this time, the bits encoded by satisfying the constraints are modulated to bits having a value of ‘1’ for an edge transited from a high level of the data pulse to a low level or from a low level to a high level, and modulated to bits having a value of ‘0’ for the interval with no pulse transition.
Accordingly, the minimum inverse period of the data pulse is expressed by (d+1)T and the maximum inverse period is expressed by (k+1)T. ‘T’ indicates a bit time interval in a record data stream. For example, in a (d, k)=(1, 7) code, the minimum inverse period (Tmin) becomes 2T and the maximum inverse period (Tmax) becomes 8T.
The recording density of the data recorded in the recording medium is increased. Thus, in the minimum inverse period (Tmin), since the minimum run (2T) is successively generated, the recorded data stream may include a distortion. That is, a focal factor and normal line slope factors of an amplitude of the 2T wave form output are smaller and more easily dispersed than a focal factor and normal line slope factors of amplitudes of other output wave forms. Thus, when the recorded data is reproduced, an error is easily generated.
When a data signal with an error is modulated, when it is recorded, it becomes a data stream including a DC component. Then, for example, when a drive of the recording medium such as a compact disk is survo-controlled, numerous error signals such as tracking errors easily appear in a form of variation or jitter.
Thus, if possible, the modulated signal should be generated without the DC components. For this purpose, a digital sum value (DSV) is controlled for a source code.
The DSV signifies a value of the sum of the data stream generated after source codes are NRZI-modulated.
A method for recording an audio signal in an optical or a magnetic optical recording carrier and reading it uses an eight-to-fourteen modulation (EFM) or an eight-to-fourteen modulation plus (EFM Plus).
The EFM-modulation signal is a code word generated as a series of 8 bit data words which are converted into a series of 14 bit code words, and 3 bits of merging words are additionally inserted thereto.
That is, each 14 bit code word should satisfy the constraint that bits having a value of ‘0’ have a minimum length (the minimum ‘0’ run length, ‘d’) of ‘2’, and bits having a value of ‘0’ have a maximum length (‘0’ run length, ‘k’) of 10 between bits having a value of the two consecutive ‘
1’s.
In addition, in order to satisfy the constraints between the code words, 3 bits of merging words are used. For example, for a possible total of eight 3-bit merging words, four 3-bit merging words can be used. That is, it may be 001, 010, 000, 100, and the remaining available 3-bit merging words (111,011,101,110) may not be used because they are against the regulation of the k (=2) constraint.
As the merging words are determined according to the regulation, low frequency components can be reduced.
However, in the digital modulating method of the conventional art, even through the input code words are converted into code words by controlling the DSV, the code word is not accurately and quickly modulated into words at a boundary between blocks constructed with the plurality of code words (that is, between the last code word of one block and the first code word of the next block).
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a digital data modulating method that is capable of quickly and accurately determining a code word to be modulated at a boundary between data blocks by using (d, k) constraints of a run length limited (RLL) code, and its apparatus.
Another object of the present invention is to provide a recording medium for storing a digital modulated data by using a digital data modulating method and apparatus that are capable of quickly and accurately determining a code word to be modulated at a boundary between data blocks by using (d, k) constraints of a run length limited (RLL) code.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a digital data modulating method in which the last unit of a block consisting of predetermined units is received and a block is obtained which does not infringe the k-constraint in the RLL code having the (d, k) constraints on the basis of a modulation data table of a predetermined unit.
In the recording medium of the present invention, the last code word of a block consisting of predetermined units is received and units are obtained and stored which do not infringe the k-constraint in the RLL code having the (d, k) constraints on the basis of a modulation data table of a predetermined code word.
To achieve the above objects, there is also pr
Ahn Seong Keun
Immink Kees A. Schouhamer
Suh Sang Woon
Birch & Stewart Kolasch & Birch, LLP
LG Electronics Inc.
Young Brian
LandOfFree
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