KR950003636B1 - Digital modulation/demodulation look-up table - Google Patents

Abstract

The look-up table includes an input means for input 8-bit data blocks, a look-up table for providing corresponding 11-bit NRZ-I signals to each 8-bit data blocks and output the corresponding 11-bit NRZ-I signal block, MSB determining section for input the output NRZ-I signal block from the look-up table and selectively inverting the MSB of the output NRZ-I signal block according to DSV (Digital Sum Value) and LSB polarity of the prior NRZ-I signal block, and output means for NRZ-I signal block of the MSB determining section.

Description

Digital Modulation / Demodulation Code Lookup Tables

1 is a block diagram showing an input / output state of a lookup table according to the present invention.

2 is a block diagram of a modulation code apparatus using a modulation code lookup table according to the present invention.

3 is a block diagram of a code demodulation apparatus using a code demodulation lookup table according to the present invention.

* Explanation of symbols for main parts of the drawings

10, 40: lookup table 20: MSB determination unit

30: MSB remover

The present invention relates to a digital modulation / demodulation coder, and more particularly, to modulate 8-bit digital data into 11-bit digital modulation code and demodulate 11-bit modulation digital code into 8-bit digital data. A modulation / demodulation code look-up table.

Conventional apparatus for recording or reproducing digital data on a magnetic recording medium using a magnetic head records the digital data on the magnetic recording medium by applying the digital data to the magnetic head through a transformer, and the digital data detected by the magnetic head. The regeneration process is performed by applying to the demodulation device through the transformer.

However, if a DC (Direct Current) component is included in the signal detected from the magnetic recording medium, the digital data is not reproduced correctly, and the bit synchronization is not smooth.

For this reason, the digital data recording / reproducing apparatus must record the digital data on the magnetic recording medium after modulation by using the DC elimination modulation code method.

The DC cancellation modulation code schemes used in the actual system are as follows.

1) M2 modulation code type

Each bit is modulated and encoded from 1 bit to 2 bits to remove direct current components from the coded signal stream and achieve smooth bit synchronization during signal reproduction.

DR (Density Ratio) of the M2 modulation coding scheme is known as "1".

2) 8-10 modulation code method

As an modulation code scheme currently used for DAT (Digital Audio Tape), an input data block consisting of 8 bits is modulated and encoded into a 10-bit codeword block by a lookup table.

When an 8-bit input data block is encoded with a 10-bit codeword block, the MSB (Most Significant Bit) of the codeword block is appropriately appropriate in some cases in order to limit the run-length and DC components of 0. Invert

In Japanese Patent Laid-Open No. 56-19506, the DR of the 8-10 modulation code is described as 0.8.

3) 8-14 Modulation Code

As a modulation coding method used in CDP (Compact Disc Player) or the like, an 8-bit input data block is changed to a 14-bit output codeword block.

To limit the DC component and limit the line-length of zero, three bits of merging bits are inserted in each block of blocks.

In Japanese Patent Laid-Open No. 61-196469, the DR of the 8-14 modulation code is described as 1.14.

However, the above-described modulation code method has the following problems.

That is, the M2 modulation coding scheme has a problem that a wide bandwidth is required because the DC component is 0 and the encoder and decoder circuits are relatively simple as compared to other modulation coding schemes, while the bit rate of data is doubled by encoding.

In the case of the 8-14 modulation code method, since the DC component is limited by the encoding and the number of 1s present between 0 becomes 2 to 10, the interference between signals is relatively small, but since the 8-bit input data increases to 14 bits, the bandwidth is increased. This increases the efficiency of coding.

In the case of the 8-10 modulation code method, since the 8-bit input data is increased to 10 bits, the coding efficiency is higher than that of the M2 code or the 8-14 code, which is 0.8, but the MSB inversion of the codeword block is limited to limit the DC component. There is a problem that needs to be determined.

The present invention has been made to solve the problems of the modulation coding scheme, and an object of the present invention is to modulate an 8-bit input data block into an 11-bit codeword block, thereby having high coding efficiency and facilitating a digital modulation process. To provide a sign lookup table.

Another object of the present invention is to provide a demodulation code table that enables easy demodulation of data modulated with an 11-bit codeword with 8-bit one data.

A feature of the present invention for achieving this object comprises: input means for inputting an 8-bit data block; The CDS is +1 and the line-length of 0 is less than or equal to 3, and has an 11-bit NRZ-I code corresponding to each of the 8-bit data blocks, and an 11-bit corresponding to the input 8-bit data block. A lookup table for outputting an NRZ-I code block; Inputting the NRZ-I code block output from the lookup table to selectively invert the MSB of the NRZ-I code block output from the lookup table according to the digital sum value (DSV) and the polarity of the LSB of the previous NRZ-I code block MSB determination unit to make; And a digital modulation code lookup table having output means for outputting an NRZ-I code block of the MSB decision unit.

Another feature of the present invention is provided with: input means for inputting an 8-bit data block; The CDS is -1 and the line-length of 0 is 3 or less, and has 11 bits of NRZ-I code corresponding to each of 8 bits of data blocks, and 11 bits of corresponding 8 bits of data block. A lookup table for outputting an NRZ-I code block; Inputting the NRZ-I code block output from the lookup table to selectively invert the MSB of the NRZ-I code block output from the lookup table according to the digital sum value (DSV) and the polarity of the LSB of the previous NRZ-I code block MSB determination unit to make; And a digital modulation code lookup table having output means for outputting an NRZ-I code block of the MSB determination unit.

Another feature of the present invention is input means for inputting 11-bit NRZ-I codes whose CDS is ± and the string-length of 0 is 3 or less; An MSB removal unit for removing MSBs of these code blocks among the 11-bit NRZ-I code blocks inputted through the input means; 11 bits of NRZ-I codes having a CDS of ± 1 and a line-length of 0 or less have 3 bits having 8 bits of data corresponding to the remaining 10 bits except for the MSB, and are input through the MSB removal unit. A lookup table for converting a 10-bit NRZ-I code into corresponding 8-bit data; And a digital demodulation code lookup table having output means for outputting 8-bit data converted from the lookup table.

Hereinafter, the definition of terms used in the present specification before describing the embodiments of the present invention will be described.

CDS (Coode word Digital Sum): A DSV calculated from the first bit to the last bit of each codeword.

DSV (Digital Sum Value): A sum obtained by adding -1 to each bit corresponding to "0" of a series of digital modulation codes and adding +1 to each bit corresponding to "1". do.

Therefore, it can be seen that the DC component is larger as the DSV is larger.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the input / output state of the 8-11 modulation code lookup table according to the present invention. The lookup table 10 has an NRZ- having a CDS of −1 and a line length of 0 or less in a block of 11 bits. Only I code blocks are selected and configured as shown in Table 1 below.

TABLE 1

In this case, the lookup table may be configured by selecting only blocks having a CDS of +1 and a row-length of 3 or less among 11-bit NRZ-I code blocks.

That is, since the 8-11 modulation code lookup table of the present invention is to convert the 8-bit input data block into 11-bit bits to remove the DC component and easily extract the clock component, the CDS of the 11-bit blocks is-. It is configured by selecting code blocks of 1 or +1 and a line-length of 0 or less.

Thus, if an 8-bit input data block is selected as an 11-bit data block whose CDS is ± 1 and a line-length of 0 or less is 3, the following table 2) will appear.

TABLE 2

In Table 2, an input 8-bit data block is represented by a binary state, but 11-bit modulation codes are represented by an NRZ-I code.

For the NRZ-I code, bit "1" indicates the occurrence of a transition (i.e. change from N to S pole or S to N state) in the magnetic recording device and "0" indicates no transition. Table 2) shows that no transition occurs every 3 bits in the case of the 11-bit NRZ-I modulation code.

As can be seen from Table 2), the 11-bit NRZ-I code block corresponding to each 8-bit input data has only one MSB different from the case where the CDS is -1 and the CDS is +1. It can be seen that the bits are identical to each other.

In this case, the 11-bit NRZ-I code modulated by the lookup table 10 has an increase in the DC component when the DSV is increased to + or-by CDS of the codes. To select the NRZ-I code when CDS is -1 when DSV is +, and the NRZ-I code when CDS is +1 when DSV is -1.

However, as described above, the 11-bit NRZ-I code with CDS +1 and the 11-bit NRZ-I code with CDS -1 differ only in the MSB, so the 11-bit NRZ-I code with CDS +1 is used. Alternatively, the 8-11 modulation code can be performed only by using a lookup table having only 11 bits of NRZ-I having CDS of -1.

For example, a case where 8-11 modulation is coded using a lookup table having only a code of NRZ-I having -1 is as follows.

First, when the DSV of the NRZ-I code modulated and encoded by the lookup table 10 is +1 and the LSB polarity of the previous NRZ-I code block is +, the NRZ-I having the CDS of -1 Since it is signed, outputting the NRZ-I code corresponding to the input 8-bit data as it is will reduce the total DSV by one.

However, if you select the NRZ-I code with CDS equal to 1 while DSV is positive and the Least Significant Bit (LSB) of the previous NRZ-I code is-, the selected NRZ-I code will eventually be inverted by +1. The state will increase the DSV by one.

At this time, inverting the MSB of the codeword causes the DSV to decrease by one because the code changes due to the characteristics of the code of NRZ-I.

Therefore, to reduce DSV when the polarity of the DSV is + and the LSB polarity of the previous NRZ-I code block is-, it will be necessary to select the NRZ-I code block when the CDS is +1.

However, in this case, since the NRZ-I code for the CDS is +1 and -1, only the MSB is different, if the lookup table is composed only of the NRZ-I code block with the CDS of -1, the CDS is -1 NRZ-I. You only need to reverse the MSB.

In addition, if the DSV is in the-state and the LSB polarity of the previous NRZ-I code is in the positive state, using the NRZ-I code with the CDS -1 will cause the DSV to increase further to-.

However, using an NRZ-I code with a CDS of + will increase the DSV by +1 and thus reduce the DC component.

Therefore, in this case, if the NRZ-I code having CDS of -1 is output from the lookup table, only the MSB of the NRZ-I code can be inverted to limit the DSV.

However, when the DSV is-and the LSB polarity of the previous NRZ-I code is-, it can be easily seen that the DSV is increased by +1 by using the NRZ-I code having the CDS of -1 as it is.

Therefore, if the MSB decision unit 20 that functions as shown in Table 3) is further connected to the lookup table 10 as shown in FIG. 2, 8-bit input data is converted into 11-bit NRZ using only the lookup table having CDS of -1. It can be easily modulated with -I code.

TABLE 3

In Table 3), N indicates that the MSB is not inverted and O means that the MSB is inverted.

The above-described configuration is an example in which the lookup table is composed of only NRZ-I codes having CDS of -1, but the lookup table 10 is composed of only NRZ-I codes having CDS of +1. The CDS selected according to the LSV polarity of the DSV and the previous NRZ-I code may be configured to properly invert the MSB of the NRZ-I code with -1.

In this way, when a signal modulated with an 11-bit NRZ-I code is reproduced and recorded on a magnetic recording medium, a lookup table for demodulating the 11-bit NRZ-I code into 8-bit one-data will be required.

However, in this case, when the CDS is +1 and when the CDS is -1, 10 bits except for the MSB are the same and the 10-bit data strings are different from each other, regardless of the state of the MSB of the 11-bit NRZ-I code. You can configure the lookup table to select the corresponding 8 bits of digital data with only 10 bits.

That is, as shown in FIG. 3, the MSB removal unit 30 is configured to remove the MSBs among the 11-bit NRZ-I codes, and the lookup table 40 has a lower 10-bit value as shown in Tables 1 and 2 above. It is configured to select 8-bit digital data blocks corresponding to each NRZ-I code block.

As such, when the 8-bit data block is modulated with an 11-bit NRZ-I code, the line-length (d, k) of 0 is (0, 3), and the maximum DSV is less than ± 2.92T as shown in Equation 10 below. Due to the limitation, it is possible to use it as a high density digital magnetic recording device code such as a digital video cassette recorder. Maximum DSV = ± (d + 1) 8 / 11T = ± 2.927 Equation 1)

In addition, since 4 (d + 1) ≥k in the digital magnetic recording apparatus, since overwriting is generally possible, the 8-11 modulation code table of the present invention has an effect of enabling overwriting.

In addition, the 8-11 modulation code table of the present invention can be easily implemented since only the CDS code is -1 or +1, and the size, weight, and cost of the modulation code device can be reduced.

Claims (3)

Input means for inputting an 8-bit data block; The CDS is +1 and the line-length of 0 is less than or equal to 3, and has an 11-bit NRZ-I code corresponding to each of the 8-bit data blocks, and an 11-bit corresponding to the input 8-bit data block. A lookup table 10 for outputting an NRZ-I code block; The NRZ-I code block output from the lookup table 10 is input according to the polarity of the digital sum value (DSV) and the LSB of the previous NRZ-I code block by inputting the NRZ-I code block output from the lookup table 10. An MSB deciding portion 20 for selectively inverting the MSB of; And a output means for outputting the NRZ-I code block of the MSB determiner (20). Input means for inputting an 8-bit data block; The CDS is -1 and the line-length of 0 is 3 or less, and has 11 bits of NRZ-I code corresponding to each of 8 bits of data blocks, and 11 bits of corresponding 8 bits of data block. A lookup table 10 for outputting an NRZ-I code block; The NRZ-I code block output from the lookup table 10 is input according to the polarity of the digital sum value (DSV) and the LSB of the previous NRZ-I code block by inputting the NRZ-I code block output from the lookup table 10. An MSB deciding portion 20 for selectively inverting the MSB of; And a output means for outputting the NRZ-I code block of the MSB determiner (20). Input means for inputting 11-bit NRZ-I codes whose CDS is ± 1 and a line-length of 0 is 3 or less; An MSB removal unit (30) for removing MSBs of these code blocks among the 11-bit NRZ-I code blocks inputted through the input means; The MSB removal unit 30 includes 8 bits of data corresponding to the remaining 10 bits except for the MSB among the 11-bit NRZ-I codes having a CDS of ± 1 and a line-length of 0 or less. A lookup table 40 for converting a 10-bit NRZ-I code input through the 8-bit data; And a digital demodulation code lookup table including output means for outputting 8-bit data converted by the lookup table (40).