JPH036923A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To form a transmission data whose low frequency band is effectively suppressed by providing a 1st low frequency suppression means suppressing a low frequency band of main information, a 2nd low frequency suppression means suppressing a low frequency band of sub information, and an output means synthesizing and outputting outputs of the 1st and 2nd low frequency suppression means. CONSTITUTION:A mapping coding circuit 12 applies mapping coding to a main information data inputted from an input terminal 10 to suppress its low frequency component. An error correction coding circuit 14 divides an output of the mapping coding circuit 12 with a generation polynomial and outputs the residue as a check bit, that is, a sub information data. Then a 8-9 conversion circuit 16 the bit of the sub information data from 8-bit into 9-bit. An addition circuit 18 adds the check bit from the 8-9 conversion circuit 16 to the main information data from the mapping coding circuit 12 to output a code word in P-bit as a whole. Thus, the transmission data whose low frequency component is sufficiently suppressed is formed and data transmission with high density is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission device for transmitting information data.

[Prior Art] Digital signal transmission systems, such as magnetic recording and reproducing systems, generally cannot reproduce DC components. Therefore, various methods have been proposed for suppressing the low-frequency components of transmission data. For example, to convert n-bit data to n-bit data, n
/n mapping coding, which can be applied when there is a correlation between adjacent data, and when adding side information such as an error detection and correction code or other additional information, it is possible to Since there is no correlation between the two, the low frequency suppression effect is low even if mapping is performed.

[Problems to be Solved by the Invention] In contrast, a method of converting m-bit data to n (>m)-bit data as an entire code word (for example, 8
-9 conversion) or a method of distributing the side information appropriately, but in the former case, for example, 8-bit data is converted to 9-bit data, which increases redundancy and causes an increase in the bit rate. There is a drawback. Also, in the latter case,
For example, a method is used in which the generated parity is distributed so that low-frequency components are suppressed, but this has the disadvantage that if the data code length is short, the amount of parity increases, making it impossible to obtain a sufficient low-frequency suppression effect. There is.

SUMMARY OF THE INVENTION An object of the present invention is to provide a data transmission device that can transmit information data having sub-information as described above while sufficiently suppressing the low frequency range.

[Means for Solving the Problems] A data transmission device according to the present invention is a data transmission device that transmits main information and sub information generated according to the main information, and suppresses low frequencies of the main information. It includes a first low frequency suppression means, a second low frequency suppression means for suppressing the low frequency range of the sub information, and an output means for combining and outputting the outputs of the first and second low frequency suppression means. It is characterized by

[Operation] The first and second low-frequency suppressing means can suppress the low-frequency range of the main information and the sub-information individually and in a method suitable for each.

Therefore, it is possible to minimize the increase in redundancy and to form transmission data that effectively suppresses the low frequency range as a whole.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic block diagram of an embodiment of the present invention. 10 is an input terminal for data to be transmitted; 12 is a mapping encoding circuit; 14 is an error correction code generating circuit;
6 converts 8-bit data to 9-bit data 8
-9 conversion circuit; 18 is an additional circuit that adds the output (sub information) of the 8-9 conversion circuit 16 to the output (main information) of the mapping encoding circuit 12; 20 is an output terminal connected to the transmission line;
2 is a clock pulse oscillation circuit, and 24 is a clock pulse oscillation circuit according to the clock pulse from the clock pulse oscillation circuit 22.
This is a timing generation circuit that generates timing signals to be supplied to 2, 14, 16, and 18.

The mapping encoding circuit 12 maps and encodes the main information data input from the input terminal 10.

If the main information data is, for example, image data, encoding is performed using its properties to suppress low-frequency components.

The error correction encoding circuit 14 divides the output of the mapping encoding circuit 12 by the generator polynomial and outputs the remainder as check bits, ie, sub information data.

Then, the 8-9 conversion circuit 16 converts this sub information data from 8 bits to 9 bits.

The 8-9 conversion circuit 16 allocates 256 pieces of 512 pieces of 9-bit digital data to 256 pieces of 8-bit digital data.
As a criterion for selecting 256 pieces of 9-bit data from 512 pieces of 9-bit data, for example, CD S (Codeword D
Select from the one with the smallest absolute value of (digital Sum). That is, with 9-bit data, CDS is +1 or -
There are 252 pieces of data that become 1, and among these, if the run length limit is 5, there are 222 pieces of data, and the remaining 34 pieces are supplemented from those with I CDS l =3. Based on these standards, 256
9-bit data of @ can be selected.

A circuit example of the 8-9 conversion circuit 16 is shown in FIG.

The conversion ROM 26 stores a conversion table between the above-mentioned 8-bit data and the selected 9-bit data, and the output of the error correction code generation circuit 14 is converted into 9-bit data by the conversion ROM 26, and the 9-bit output is ,parallel·
It is converted into a serial signal by the serial conversion circuit 28,
It is converted into an NRZI code by the NRZI conversion circuit 30. This NRZ I code is supplied to an additional circuit 18.

The addition circuit 18 adds the check bits, that is, the sub information data (L bits) from the 8-9 conversion circuit 16 to the main information data (K bits) from the mapping encoding circuit 12,
A total of P bits of code words are output. The output configuration of the additional circuit 18 is shown in FIG.

In this way, it is possible to form transmission data that sufficiently suppresses low-frequency components for both the main information data and the sub-information data generated according to the main information data, enabling high-density data transmission. Become.

8-9 conversion, more generally m-n conversion, increases the redundancy in the side information data part, leading to an increase in the transmission bit rate, but this effect is limited to only the side information data, so the transmission bit rate increases. The increase in rate is minimal. Furthermore, the method for suppressing low-frequency components of the sub information data is not limited to 8-9 conversion, but may be any other conversion method.

[Effects of the Invention] As can be easily understood from the above description, according to the present invention, low frequency components of both main information and sub information can be suppressed sufficiently effectively.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of an embodiment of the present invention, and FIG.
The figure shows an example of the circuit configuration of the 8-9 conversion circuit 16, and FIG. 3 is a diagram showing the data frame structure of the output of the additional circuit 18.

Claims (1)

[Claims] A data transmission device that transmits main information and sub-information generated according to the main information, comprising a first low-frequency suppressing means for suppressing low frequencies of the main information, and a first low-frequency suppressing means for suppressing low frequencies of the sub-information. 2
1. A data transmission device comprising: low frequency suppression means; and output means for combining and outputting the outputs of the first and second low frequency suppression means.