JPH02228131A - Code converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a code conversion device that converts any information word written in binary values of l and 0 into a channel code suitable for recording and transmission.

BACKGROUND OF THE INVENTION In recent years, code conversion devices have become indispensable for digital recording and communication.

An example of the above-mentioned conventional code conversion device will be described below with reference to the drawings.

Figures 4 and 5 show variation II in a conventional code conversion device.
I! The binary information word that represents the rule, that is, shown in FIG. 5 according to the conversion rule shown in FIG. 4, is 010010001001QOOOOOO100OOOO
It can be converted to a channel code such as 100OO100O. This conversion method is called (2,7) conversion, and is a conversion method frequently used in magnetic recording and the like.

(For example, U.S. Pat. No. 3,689,899) R problem to be solved by the invention However, in the above method, the number of 1's and the number of O's in the channel code are generally not equal, so it is difficult to solve the problem, especially for optical discs. When this is directly recorded, there is a problem that DC drift occurs in the reproduced signal when it is reproduced after being recorded on the medium, and it is easy to make an error when determining whether it is 1 or 0 based on the reproduced signal. In other words, the reproduction signal of an optical disk originally contains low-frequency noise components such as DC drift caused by differences in the reflectance of the medium surface and differences in recording sensitivity during recording, and this must be removed before demodulation. be. However, in this (2,7) conversion method, since the reproduced signal itself also has low frequency components, it is difficult to separate the two, making it susceptible to the influence of low frequency noise components and causing reading errors. .

In view of the above-mentioned problems, the present invention provides a code conversion device and decoupling device that is less susceptible to low frequency noise. It provides:

Means for Solving the Problems In order to solve the above problems, the code conversion device of the present invention converts an M-bit information word into an N-bit channel code where N>M, and the N-bit channel code is , all channel codes classified into groups have an equal number of 1's, and there are always at least two 1's adjacent to each other, and there are also at least two O's adjacent to each other. is ensured to exist.

According to the above-described structure, the number of 1's included in each channel code belonging to each group is determined to be a predetermined number, so that the channel bits of the input channel code are sorted in descending order of likelihood. By determining only a predetermined number of bits as 1, it is possible to determine whether each channel bit is 1 or 0 without being affected by low-frequency noise such as DC drift, allowing accurate reading of channel codes. . Furthermore, since there are always consecutive l and consecutive O in one channel code,
The maximum and minimum values of each channel code can be made almost constant, and as a result, the reproduced channel code can be easily standardized, reducing the burden on subsequent processing circuits such as the likelihood judgment circuit. It is possible to reduce this.

The basic concept of the invention will be explained in more detail below.

When converting an M-pit information word into an N-bit channel code where N>M, if the conversion rule is determined so that the number i of l included in each channel code is always a predetermined number, the input The channel code can be accurately read from the channel signal. This is because a channel signal can be sampled for each channel bit, and a predetermined number of bits can be determined to be 1 from the sampled values in descending order of likelihood. In this way, sample values for each bit are relatively compared in channel code units, making it less susceptible to low frequency noise components. These codes are generally i-out
It is called the -o f-N (I-o-of-N) code. Once the number M of bits of the information word is determined, the minimum number N of bits of the channel code that allows such conversion is uniquely determined.

Table 1 shows the correspondence between M, N, and i.

Table 1 Here, M, N, and i are determined as the combination that satisfies NCt≧2M such that N is the minimum for each M.

On the other hand, the smaller the ratio of N7M, the better the efficiency of transfer using the channel code.
The value of can be made even smaller than that shown in Table 1. However, if the multiple allowable values for the number l are too close together, it becomes difficult to distinguish between them, and reading errors are likely to occur. It has been found that the number of 1's included in the input channel code can be accurately identified if the plurality of allowed values are 3 or more apart from each other. Therefore, Table 2 shows an example in which two numbers of l are set at a distance of 3 or more from each other and each is represented by i and j.

Table 2 Here, M N, t, j satisfies 1, C, + , C, ≧ 21'I, and when compared with Table 1, it can be seen that N for each M is smaller by l. In this way, it is possible to efficiently convert the code into a channel code and to read the input channel signal accurately.

Embodiment Hereinafter, a code conversion device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of a code conversion device according to a first embodiment of the present invention. In Figure 1, 10
is a converter, 1.2 and 3 are conversion tables, and converter 1
0 converts (M-) 8-bit information word XXXXXXXXX input according to conversion tables 1.2 and 3 to (N-
) 10 pit channel code yyyyyyyyyy
Convert to

The operation of the binary information conversion method configured as above will be explained below with reference to FIGS. 1 and 2.

First, FIG. 2 is a conceptual diagram showing an example of the operation of this embodiment.

In the figure, C1 is a channel code belonging to the first group,
This corresponds to 250 8-bit information words from oooooooooo to 1l111001. C2, C3
are the second. It is a channel code belonging to the third group, 11111010.11111011.11111
100.11111101.11111110.111
It corresponds to 6 types of information words: 11,111. For channel codes belonging to the first group, the number of 1's in the IO bit data is always 5, that is, 5-out-of-10,
It is associated with the corresponding information word by the conversion table l. 1 included in the channel code belonging to the second group
The number of l included in the channel code belonging to the third group is 8 (8-out-of-10)%.
-of-10) and are associated with corresponding information words by conversion tables 2 and 3, respectively.

Here, for convenience, the information words corresponding to the first group of channel codes will be referred to as normal information words, and the information words corresponding to the second and third group channel codes will be referred to as specific information words.

As shown in FIG. 2, it is assumed that an information word consisting of 8 information bits is manually inputted sequentially from the top.

Since the first three words are normal information words, conversion table 1
The information words input at the 0th order, which are respectively converted into channel codes (CI in the figure) belonging to the first group according to the following, are specific information words. For a specific information word, there are two channel codes, one belonging to the second group and one belonging to the third group.
The second group or the third group is alternately selected and converted into the corresponding channel code. Here, first, the zero-order information word that is converted into the second group of channel codes (02 in the figure) is a normal information word, so it is converted into the first group of channel codes. Next, a specific information word is input again, but since the previous specific information word has been converted to the channel code of the second group, this time the corresponding channel code in the third group (C3 in the figure) is converted to In this manner, the converter 10 operates to alternately convert a particular information word into a second group of channel codes and a third group of channel codes. In this way, the number of 1's included in the channel code of the second group is 2, and the number of 1's included in the channel code of the third group is 8, so the average is 5, and the number of 1's included in the channel code of the first group is 8. Since it is equal to the number of 1s included in the code,
The number of occurrences of 1 in the channel code is constant on average, resulting in a so-called DC-free channel code.

Here, the structure of the conversion table will be explained. Currently, there are 2"-256 information words that can be written in 8 bits. On the other hand, there are 2"-256 information words that can be written in 8 bits. On the other hand, it contains 5 each of 1 and O (5-out- o r-10),
The number of channel codes that can be written with lO bits is: C,=252 ways. Therefore, conversion table 1 alone cannot support all 8-bit information words, and conversion tables outside this constraint are required for the remaining four types of information words.

However, in this embodiment, there are 250 ways to express 5-out-of-10, and the remaining 6 ways are special codes 2-out-of-10 or 8-out-of-10.
It is converted to -10. This is 5-out-of-1
1010101 of the channel codes expressed as 0
This is because 010 and 0101010101 were excluded.

In a 5-out-or-10 code, except for these two, there are always two or more adjacent 1's and two or more adjacent 0's. For a channel code to be directly recorded on a medium or transmitted in this form, the presence of both 1 and 0 pairs has an important meaning, which will be explained with reference to FIG.

Whether recording or transmitting information, the capacity of a recording medium or transmission line is limited, and it is common practice to make the most of that capacity, even if it means going to some extent. In other words, when the recording density of the recording signal or the transmission frequency of the transmission signal is increased to about the cutoff point, signals with high frequency components are recorded or transmitted in a somewhat degraded state.

The 5-outof-10 code generally consists of frequency components of various high and low frequencies, but 1010101010 and 01
Only 01010101 contains only the highest frequency component, 1010101010 and the other 5-out-or
-10 code, for example 1011001010, is actually used as a recording signal, the reproduced waveform is shown in Figure 3 (a
) and (b), respectively. In the former, all bits have deteriorated (in this case, the amplitude has decreased), while in the latter, since it has a double period component such as 1100, etc., that part There is little deterioration.

To put it another way, the 5-out-of-10 code has periodic components with a double period or more, such as 1100, if you exclude 1010101010 and 0101010101, so the amplitude within the l code (Maximum value - Minimum value) is always constant. Therefore, it is convenient when normalizing the amplitude, such as applying AGC to such a reproduced signal, and sampling the amplitude for each code. , it would be a good idea to provide feedback on this. Conversely, 1010101010 and 010
If there is 1010101, the amplitude will drop by that code, and if they are consecutive, the AGC
This has the disadvantage that the gain of the signal increases unnecessarily.

Conversion table 2 and conversion table 3 are in this 10101
It provides conversion rules for six channel codes including 01010 and 0101010101. According to conversion table 2, 1111 of the 8-bit information words
2 specific information words from 1010 to 11111111
-out-of-10. The corresponding information words are 6
Since there are only a few 1's, the conversion table 2 can be configured only with channel codes in which two 1's are always adjacent. In this way, the amplitude of 2-out-of-10 does not need to be reduced.

Conversion table 3 associates the above-mentioned six specific information words with channel codes obtained by inverting the logic of the channel codes in conversion table 2. If we consider the logic inverted, then in the case of conversion table 2 Since it is the same as , the explanation will be omitted.

Effects of the Invention As described above, the present invention converts an M-bit information word into an N-bit channel code where N>M, and furthermore, the N-bit channel code is classified into a plurality of groups, and the N-bit channel code is classified into the same group. All channel codes to be used have an equal number of 1's, and two or more 1's are always adjacent to each other.
Furthermore, since two or more zeros are always adjacent to each other, it is possible to determine whether each channel bit is 1 or 0 without being affected by low-frequency noise such as DC drift or envelope fluctuations. Therefore, the channel code can be read accurately.

Furthermore, M=8. By setting N-10, i=5,
The conversion is efficient and the processing is not very complicated.
This has the effect that byte-by-byte processing becomes easier.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a code conversion device according to an embodiment of the present invention, FIGS. 2 and 3 are conceptual diagrams showing its operation, and FIGS. 4 and 5 are conceptual diagrams explaining the operation of a conventional example. It is a diagram. 1.2 and 3...conversion table, 10...
Converter, 11, 12. 13 Inverse conversion table, 14 Binarization means, 20
・Inverse converter. Agent's name Patent attorney Shigetaka Awano 1 person 8 pits fi + 10 Pimo Noto Figure !! Figure Figure Figure

Claims (3)

[Claims] (1) A code conversion device that converts an information word consisting of M bits of information bits into a channel code consisting of N bits of channel bits larger than M, wherein the channel codes are classified into a plurality of groups and the same group The channel codes classified as
1. A code conversion device characterized in that there are always 1's and at least two 0's adjacent to each other are always present. (2) The code conversion device according to claim (1), wherein N is an even number and a certain group includes N/2 1's. (3) N=10 and 10 from the group containing 5 1s
3. The code conversion device according to claim 2, wherein 10101010 and 0101010101 are excluded.