JPH0518487B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a data error detection circuit built into a signal processing circuit used in a compact disc (CD) playback device.

(b) Conventional technology A CD playback device creates 8-bit symbols from data read out from a disc in the form of an EFM signal and restores music signal data, but data errors occur in these symbols. Sometimes. This is caused by defects when pits are written on the disc, defects caused by scratches etc. that occur during handling of the disc, or defects caused by mechanical fluctuations or disturbances in the playback device. Therefore, in order to detect and correct data errors, a system called a cross-linterleaved Reed-Solomon code (CIRC) is used in CDs.

This method will be briefly explained. First, when recording data on a disk, 6 pieces of 16-bit music signal data for each of the right channel and left channel are converted into 8 bits each.
Divided into bit symbols, a total of 24 symbols are created. After being selectively delayed and recombined, they are based on Reed-Solomon coding.
Parity data Q ₀ , Q ₁ , Q ₂ , Q ₃ (8 bits each) of C ₂ is attached. Furthermore, these 28 symbols are
Parity data P ₀ , P ₁ , P ₂ , P ₃ (8 bits each) of C ₁ are created and added similarly based on the Reed-Solomon coding method, each delayed by a different time. Then, a total of 32 symbols are selectively delayed, among which parity data Q ₀ , Q ₁ , Q ₂ ,
_Q3 , _P0 , _P1 , _P2 , and _P3 are inverted to form a data group for writing, which is EFM (8-14 modulation) modulated and recorded on the disk together with a frame synchronization signal.

Also, when playing a disc, the read
Thirty-two 8-bit symbols are created from the EFM signal, and these are processed in the opposite way as they were recorded.
That is, the 32 symbols are selectively delayed and parity data Q ₀ , Q ₁ , Q ₂ , Q ₃ and P ₀ , P ₁ , P ₂ ,
_P3 is inverted and _C1 decoded. In the _C1 decoding process, a syndrome is calculated based on each symbol, and error detection and error correction are performed from the calculated syndrome according to the Reed-Solomon coding method. Further, the 28 symbols subjected to _C1 decoding are each delayed for a different time and then subjected to _C2 decoding. Similarly, the _C2 decoding process is
A syndrome is calculated from each symbol, and error detection and error correction are performed based on the calculated syndrome according to the Reed and Solomon coding methods. and,
The 24 symbols after the _C2 decoding process are rearranged and selectively delayed, and then returned to the original music signal data.

The CD system using the cross-interleaved Reed-Solomon coding method was introduced in 1982.
It is described in detail on pages 103 to 110 of the ``Illustrated Compact Disc Reader'' (Ohmsha) published on November 25, 2017.

Conventionally, when detecting errors based on the Reed-Solomon coding method, syndromes are calculated according to the following equation.

S ₀ S ₁ S ₂ S ₃ =1 1…1 1 α ³¹ α ³⁰ …α 1 α ⁶² α ⁶⁰ …α ² 1 α ⁹³ α ⁹⁰ …α ³ 1D ₀ D ₁ 〓 D ₃₁ …(1) In addition, α is the root of the 8th degree primitive polynomial F(X)=X ³ +X ⁴ +X ³ +X ² +1.

As a result of the above calculation, the syndromes S ₀ , S ₁ , S ₂ , S ₃
If all are "0", it is determined that there is no error.

On the other hand, if there is an error only in the j-th data D _j , S ₁ ² = S ₀ · S ₂ , S ₂ ² = S ₁ · S ₃ S ₀ ≠ 0, S ₁ ≠ 0, S ₂ ≠ The error data position is determined by calculating _{S 1 /} S ₀ =α ^j and taking the logarithm thereof.

Moreover, if there is an error in data D _j and D _i , α ^j + α ⁱ = S ₁・S ₂ + S ₀・S ₃ /S ₁ ² +S ₀・S ₂ α ⁱ +α ^j =S ₂ ² +S ₁ ·S ₃ /S ₁ ² +S ₀ ·S ₂ 0≦j, i≦31, j≠i hold, so that when j and i are determined, it is determined that there is a double error. Furthermore, the data errors E j and _{E i are} determined by E _j E _i =1/α ^j +α ^j S ₁ +α ⁱ ·S ₀ S ₁ +α ^j ·S ₀ .

Regarding CD data error detection and correction using the above-mentioned Reed-Solomon coding method, please refer to Japanese Patent Application Laid-open No. 1989-
It is described in detail in Publication No. 77529.

(C) Problems to be Solved by the Invention However, the circuit for detecting and correcting data errors described above requires a ROM for logarithmic conversion and a large number of multiplication/division circuits, and this is especially difficult when performing double error detection. In addition, since multiplication and division must be repeated, it takes time to detect errors and calculate error positions, and the number of timing signals required for calculations increases.

(d) Means for solving the problems The present invention has been made in view of the above-mentioned points, and it is possible to determine the syndrome S ₀ ,
S ₁ , S ₂ , S ₃ are calculated, and the syndromes S ₀ ,
Syndrome calculation means that divides S ₁ , S ₂ , S ₃ by 1, α, α ² , α ³ (α is the root of an 8th order primitive polynomial) and syndromes S ₀ , S ₁ , S ₂ , S ₃ are all an error zero detection means for detecting "0"; a counting means for counting and holding the number of times j divided by 1, α, α ² , α ³ by the syndrome calculation means; and a result S ₀ ' of the calculation means. ，
Based on S ₁ ′, S ₂ ′, S ₃ ′, S ₀ ′+S ₁ ′, S ₁ ′+S ₂ ′,
_an addition means _for calculating S ₂ ′+S ₃ ′;
a single error _detection means for detecting that S ₁ ′+S ₂ ′, S ₂ ′+S ₃ ′ are all “ ₀ ”;
_A ⁽ _{= _ _ _ _} ^_ _{_ _} ^_ i-j, i, j are error positions)
double error detection means for detecting, error position calculation means for calculating i from j held in the counting means and the a, and error calculation means for calculating an error component based on the S ₀ ′+S ₁ ′ and a. It is equipped with the following.

(E) Effect According to the above-mentioned means, the syndrome calculation means multiplies the symbols by 1, α, α ² and α ^3, respectively, depending on the timing at which the symbols are sequentially applied.
By calculating the sum of the multiplication result and the symbol to be applied next, and further multiplying the sum by 1, α, α ² and α ³ , the above-mentioned equation (1) is calculated, and the syndrome S ₀ , Find S ₁ , S ₂ , and S ₃ . If the calculated syndromes S ₀ , S ₁ , S ₂ , and S ₃ are all "0", the error zero detection circuit determines that all the read data are correct. On the other hand, if there is an error, the calculation means calculates the syndromes S ₀ , S ₁ ,
The operation of dividing S ₂ and S ₃ by 1, α, α ² and α ^3, respectively, and then dividing the previous calculation result by 1, α, α ² and α ³ at the next timing is repeated. Furthermore, each time this division is executed, based on the division results S ₀ ′, S ₁ ′, S ₂ ′, S ₃ ′, the addition means calculates S ₀ ′+S ₁ ′, S ₁ ′+S ₂ ′, S ₂ ′+S ₃ ′ is obtained, and S ₀ ′+S ₁ ′, S ₁ ′+S ₂ ′, and S ₂ ′+S ₃ ′ are applied to the single error detection means and also applied to the double error detection means. be done. Further, the number of divisions is counted and held in a counting means. That is, when the single error detection means detects S ₀ ′ + S ₁ ′ = S ₁ ′ + S ₂ ′ = S ₂ ′ + S ₃ ′ = 0, it is detected that there is one data error, and that The error position j can be determined based on the contents of the counting means at that time. In addition, the double error detection means detects two data errors by the detection output when S ₀ ′+S ₁ ′=S ₁ ′+S ₂ ′/α ^a =S ₂ ′+S ₃ ′/α ^2a . Difference a between the error position and the error position
(=ij) is determined, and the error position j can be determined based on the contents of the counting means at that time. Then,
The error position calculating means can determine the error position i from a and j. On the other hand, if no detection is performed, three or more errors have occurred, and in this case, correction is impossible. By each means acting in this manner, error detection can be easily performed with a small number of timing signals.

(f) Embodiments First, before explaining embodiments, data error detection of the present invention will be explained. For _C1 error detection,
Syndrome can be calculated from symbol using equation (1) mentioned above.
S ₀ , S ₁ , S ₂ , and S ₃ are determined, and in the case of the present invention, equation (1) is rewritten as follows.

_{This is _ _} ^{_ _ _ _ _ _ _ _} _{_ _ _} , the subscripts of symbols D ₀ to _{D 31} in equation (1) are reversed, and the symbol in equation (1)′ is
D ₃₁ is the actual symbol D ₀ . That is, the actual symbols are D ₀ ,
D ₁ , D ₂ ...D ₃₁ , but in the present invention, conversely,
Since D ₃₁ , D ₃₀ . . . D ₀ are used, the addresses are so-called reversed.

If there is no error in symbols D ₃₁ to _{D 0} , syndromes S ₀ , S ₁ , S ₂ , and S ₃ will all be “0”. However, if an error occurs in symbols D _i and D _j (j≦i), the syndrome is S ₀ = E _i + E _j S ₁ = α ⁱ E _i + α ^j E _j S ₂ = α ²ⁱ E _i + α ^2j E _j S ₃ = α ³ⁱ E _i + α ^3j E _j ...(2). Note that E _i and E _j are each error components.

When these calculated syndromes S ₀ , S ₁ , S ₂ , S ₃ are divided by 1, α, α ² , α ³ j times, respectively, S ₀ ′,
Suppose that S ₁ ′, S ₂ ′, and S ₃ ′ become, becomes. Therefore, from equation (3), S ₀ ′+S ₁ ′=E _i (1+α ^ij )…(4) S ₁ ′+S ₂ ′=α ^ij E _i (1+α ^ij )…(5) S ₂ ′+S ₃ ′ =α ^2(ij) E _i (1+α ^ij ) …(6) is obtained.

Here, in the case of a single error, assuming that i=j and E _i =0, equations (4), (5), and (6) become S ₀ ′+S ₁ ′=S ₁ ′+S ₂ ′=S ₂ ′+S ₃ '=0...(7) Therefore, a single error can be detected by detecting that equation (7) holds true. Note that the error position is indicated by the number j of times the syndromes S ₀ , S ₁ , S ₂ , and S ₃ are divided, and the error component E _j is the value of the syndrome S ₀ .

On the other hand, in the case of double error, from equations (4), (5), and (6), S ₀ ′+S ₁ ′=S ₁ ′+S ₂ ′/α ^ij =S ₂ ′+S ₃ ′/α ^2(i
-j) …(8) is required. In equation (8), if i-j=a, since i and j are both 0 to 31, 1≦a≦31
becomes. Therefore, S ₁ ′+S ₂ ′ and S ₂ ′+S ₃ ′ are α,
A double error can be detected if equation (8) holds when divided by α ² a times. Also, the error position i is a+j
It can be found by Furthermore, the error component E _i is
From equation (4), E _i =S ₀ ′+S ₁ ′/1+α ^ij …(9) is obtained. In equation (9), 1+α ^ij can be converted to α ^x in the Galois field, converting the above a to α ^x to obtain E _i , and further, S ₀ = E _i +
It is determined from E _j by E _j =S ₀ −E _i .

Single error correction is performed by adding error component E _j to the symbol at detected error position j,
Double error correction is performed by adding error components E _i and E _{j to the symbols at detected error positions i and j} , respectively.

FIG. 1 is a block diagram showing an embodiment of the present invention that implements the above-described error detection. In Figure 1, RAM1 is read from disk and EFM
Symbols D ₀ to _{D 31} of each converted frame
(The subscript indicates the actual address order) are written in a predetermined order by an address control circuit (not shown), and are read out during error detection and correction of _C1 and _C2 and when outputting to DA conversion. and a memory to which data is written, and is connected to an 8-bit data bus 2. Syndrome calculation means 3, 4, 5, and 6 are each connected to the data bus 2, and the symbols sequentially read out from the RAM 1 are connected to the data bus 2.
Input D ₃₁ to _{D 0} (the subscripts are the reverse addresses of the actual addresses, and the reverse addresses will be used below), perform the calculation of equation (1)′ mentioned above, and calculate the calculated syndrome S ₀ , S ₁ , S ₂ , and S ₃ are divided by 1, α, α ² , and α ^3, respectively, to calculate S ₀ ′, S ₁ ′, S ₂ ′, and S ₃ ′.
Moreover, the syndrome calculation means 3, 4, 5, 6 are
A clock pulse created by the timing signal SYRAM that reads symbols D ₃₁ to _{D 0} from RAM1 and the timing signal SYNDCL that executes division.
It operates using SCLK, and switching between syndrome calculation and division is performed using a control signal SCONT. The addition means 7, 8, and 9 are the syndrome calculation means 3, respectively.
Input the outputs S ₀ ′, S ₁ ′, S ₂ ′, S ₃ ′ of 4, 5, and 6,
It outputs S ₀ ′+S ₁ ′, S ₁ ′+S ₂ ′, and S ₂ ′+S ₃ ′, and performs a modulo 2 sum by E-OR of each bit. The respective outputs of the adding means 7, 8 and 9 are applied to error detection means 10, single error detection means 11, and double error detection means 12. The error zero detection means 10 detects the syndromes S ₀ , S ₁ , S ₂ ,
At the time when S ₃ is calculated, when it is detected that S ₀ = 0 and S ₀ + S ₁ = S ₁ + S ₂ = S ₂ + S ₃ = 0, the symbols D ₃₁ to D ₀ are It determines that there is no error and outputs signal ZE. On the other hand, the single error detection means 11 includes the syndrome calculation means 3,
Syndrome S ₀ , S ₁ , calculated in 4, 5, 6
Each time S ₂ , S ₃ is divided by 1, α, α ² , α ³ , it is detected that Equation (7) holds true, and if Equation (7) holds, a single error occurs in the symbol. Detection output 1E is output as hot. The double error detection means 12 includes syndrome calculation means 3, 4, 5,
Each time division by 6 is performed, it is detected that equation (8) holds true, and S ₁ ′+S ₂ ′ is divided by 1/α ^a , and S ₂ ′+S ₃ ′ is divided by 1/α ^2a Divide by and divide the division result and S ₀ ′ + S ₁
By detecting a match of ', it is possible to determine that there is an error and to obtain error location information a=ij. Then, the double error detection means 12 indicates error position information a.
32 detection outputs a _ij are output. That is, if there is an error in D _i and D _j of symbols D ₃₁ to _{D 0} , (3)
As is clear from equations (8) to (8), the syndrome S ₀ ,
When dividing S ₁ , S ₂ , S ₃ by 1, α, α ² , α ³ j times,
Only one of the 32 detection outputs a _ij becomes "1".
However, if there is a triple error or more,
While the syndrome calculation means 3, 4, 5, and 6 perform division 31 times, the detection output appears multiple times in the detection output a _ij . The detection output _aij is a 32-bit D-
is applied to the a register 13 consisting of FF and
a ₀ (when i=j) is applied to the OR gate 14, and the output of the OR gate 14 is the error detection output 2E.
is output as The counting means 15 counts the timing signal SYNDCL that causes the syndrome calculation means 3, 4, 5, and 6 to execute division by 1, α, α ² , α ³ , and calculates the number of times the division has been performed. A counter 16 and the output of the counter 16 are applied,
It is composed of a register 17 consisting of a 5-bit D-FF for storing the count contents. The latch pulse generating means 18 outputs an OR from the detection output 1E from the single error detection means 11 and the double error detection means 12.
The detection output 2E outputted through the gate 14 is applied, and the OR gate 19 outputs a pulse jLP that causes the count contents of the counter 16 to be held in the 5-bit register 17 based on the respective detection outputs 1E and 2E. Further, the pulse jLP is an 8-bit D-FF that stores and holds the output S ₀ ' of the syndrome calculation means 3.
A register 20 consisting of a register 20 stores the detection output a _ij
A register 21 consisting of a 32-bit a register 13 and an 8-bit D-FF that stores S ₀ '+S ₁ '
It becomes the clock. Further, a latch pulse output from the latch pulse generating means 18 based on the detection output 2E is applied to the uncorrectable determining means 22.
The uncorrectable determination means 22 determines that there is a double error when the number of applied latch pulses is one, and instructs the correction control means 23 to perform correction, and also causes the flag control means 24 to set the C ₁ or C ₂ flag. It outputs a control signal 2ESIG that instructs addition, and if two or more latch pulses are applied, it determines that there is a triple error or more, and instructs the correction control means 23 to prohibit correction, and flag control means 24 to C ₁
Alternatively, it outputs a control signal NG instructing to add the _C2 flag to the flag register 25. The detection output ZE from the zero error detection means 10 is applied to the latch pulse generation means 18, the uncorrectable determination means 22, and the correction control means 23, and if no error is detected, these operations are prohibited. Ru. Detection output held in a register 13
The encoder 26 to which a _ij is applied converts the 32 signals into 5-bit binary data, and the converted 5-bit data is applied to the error position calculation means 27. The error position calculation means 27 calculates the data held in the register 17 of the counting means 15,
That is, the syndromes S ₀ , S ₁ , S ₂ , S ₃ are set to 1, α,
This is an addition circuit that adds the number of times j divided by α ² and α ³ and the 5-bit data of ij to calculate the error position i. Output i (5 bits) of error position calculation means 27
and the output j of register 17 are both inverter 2
8 and 29, selected by the multiplexer 30, and supplied to the address control circuit of the RAM1. That is, error positions i and j are used to specify the address of a symbol where an error has occurred and to correct the symbol. Here, the reason why the data i and j are inverted by the inverters 28 and 29 is to restore the addresses of the symbols D ₀ to D ₃₁ which have been given in reverse, as described above.

The error calculation means 31 inputs S ₀ '+S ₁ ' stored in the register 21 and the error position information a _ij stored in the a register 13, and calculates the error component of the symbol at the error position i based on equation (9). This is to calculate E _i , and 1
A decoder method is used to convert +α ^ij to α ^x ,
Calculations are simplified. The addition means 32 calculates the sum of the error components E _i and E _j S' ₀ (equal to the syndrome S ₀ ) and the error component E _i calculated by the error calculation means 31.
, and the error component E _j is calculated by E-OR for each bit. The calculated error components E _i and E _j are each input to the multiplexer 3.
3 and is selectively outputted by the same control signal SEL as the multiplexer 33. That is, when multiplexer 30 selects and outputs error position data i, error component E _i is output from multiplexer 33, and when error position data j is selected, error component E _j is selected. An adder 34 to which the output of the multiplexer 33 is applied and a register 35 consisting of an 8-bit D-FF perform error correction, and the error position data i or the register 35 selected from the multiplexer 30 and applied to the address control circuit The error symbol D _i or D _j read from RAM1 based on j is stored in register 3.
5, and in the adding means 34, the error symbol D _i or D _j and the error component E _i or E _j are summed modulo 2, and the addition result, that is, the corrected symbol is again Stored at the same address in RAM1. The operation of the addition means 34 is controlled by the control signal ENA output from the correction control means 23, and the addition operation is not performed in the case of no error and uncorrectable error, and in the case of a single error and double error. An addition operation is performed.

The error detection and correction circuit described above is C ₁
This circuit is used for both error detection and correction and _C2 error detection and correction, but in the case of _C2 error detection and correction, the number of symbols is 28 from _D0 to _D27 , so the syndrome Arithmetic means 3, 4, 5, 6
The number of timings for calculating the syndromes S ₀ , S ₁ , S ₂ , and S ₃ is 28, and the number of times of division by 1, α, α ² , and α ³ is 27. Therefore, during the _C2 error detection and correction period, the counter 16 is first preset to "4". Details regarding this point will be described later.

Next, main specific examples of the circuit shown in FIG. 1 will be explained below.

FIG. 2 shows syndrome calculation means 3, 4, 5,
6, which includes an E-OR gate 36 to which each bit _b0 to _b7 of the symbol sent to the data bus 2 is applied, and eight gates to which the output of the E-OR gate 36 is applied. D-FF37 and D-FF
37, and ^a multiplexer 40 that selects the output of each of the ^arithmetic elements 38 and 39 and applies it to each input of the E-OR gate 36. configured. D-
The FF 37 operates with the clock pulse SCLK generated by the timing signal SYRAM and the timing signal SYNDCL mentioned above, and the multiplexer 40 calculates the syndromes S ₀ , S ₁ , S ₂ , S ₃ and 1, α, α ² ,
It is controlled by a control signal SCONT that switches between dividing and dividing ^α3 . That is, when calculating the syndromes S ₀ , S ₁ , S ₂ , and S ₃ , the α ⁿ calculation element 38 is used,
When calculating S ₀ ′, S ₁ ′, S ₂ ′, and S ₃ ′ by division, the 1/α ⁿ calculation element 39 is used.

By the way, in the syndrome calculation means 3, (1)'
As is clear from this, syndrome S ₀ is a symbol
Since it is the sum of D ₃₁ to _{D 0} , and S ₀ ' is S ₀ divided by "1", the arithmetic element 38 is α ⁰ ,
Arithmetic element 39 is 1/α ⁰ . That is, in the case of the syndrome calculation means 3, the calculation elements 38, 39 and the multiplexer 40 are unnecessary, and the D-FF 37
It is sufficient to directly apply each of the outputs Q ₀ to Q ₇ to the E-OR gate 36. Therefore, the timing signal SYRAM for sequentially reading symbols D ₃₁ to D ₀ from RAM1
As a result, the first read symbol _D31 becomes D-
Symbol input to FF37 and then read out
D ₃₀ is the output of D-FF37, that is, D ₃₁ and E-OR
At the gate 36, modulo 2 is added and converted to D-FF.
It is held at 37. Repeat this action 32 times (from D ₃₁ to D ₀
By repeating this process until symbol _D0 is read out, the output of the D-FF 37 becomes syndrome _S0 .

Further, in the syndrome calculation means 4, the calculation element 38 is α, and the calculation element 39 is 1/α. This α calculation element 38 is, as shown in FIG. 3a,
Inputs I ₀ to I ₇ and outputs O ₀ to O ₇ are connected, and three E-
An OR gate 41 is provided, and
As shown in FIG. 3b, the 1/α calculation element 39 has inputs I ₀ to I ₇ and outputs O ₀ to O ₇ connected to each other, and is also provided with three E-OR gates 42. .
Therefore, in the syndrome calculation means 4, the symbol D ₃₁ first read out from the RAM 1 and stored in the D-FF 37 according to the timing signal SYRAM is
As the multiplication result of αD ₃₁ by α calculation element 38, E
− applied to OR gate 36 and then symbol D ₃₀
When is read out, αD ₃₁ +D ₃₀ is added in the E-OR gate 36, and the result is stored in the D-FF 37. By repeating this operation 32 times, the syndrome S ₁ shown in equation (1)' is calculated and output from the outputs Q ₀ to Q ₇ of the D-FF 37. On the other hand, each time one timing signal SYNDCL is applied with the 1/α calculation element 39 selected and the inputs b ₀ to b ₇ of the E-OR gate 36 set to “0”, the signal held in the D-FF 37 is Syndrome S ₁
is multiplied by 1/α by the 1/α calculation element 39 and held in the D-FF 37, and the outputs Q ₀ to Q ₇ become S ₁ '=S ₁ /α.

Therefore, by sequentially applying 31 timing signals SYNDCL, S ₁ ' from S ₁ /α to S ₁ /α ³¹ can be calculated.

Furthermore, the arithmetic element 38 of the syndrome arithmetic means 5
is α ² and the arithmetic element 39 is 1/α ² . This α ² calculation element 38 is an element having the input/output relationship shown in FIG. 3C, and is a two-stage series connection of the α calculation elements shown in FIG. 3A. On the other hand, the 1/α ² arithmetic element 39 is an element having the input/output relationship shown in FIG. 3d, and is also a two-stage series connection of the 1/α arithmetic elements shown in FIG. 3b. Further, the arithmetic element 38 of the syndrome arithmetic means 6 is α ³ and the arithmetic element 39 is 1/α ³ . The α ³ arithmetic element has three stages of elements 3a connected in series, and the 1/α ³ arithmetic element has three stages of elements 3a connected in series.

Both syndrome calculation means 5 and 6 calculate the syndromes S ₂ and S ₃ of equation (1)′ using the timing signal SYRAM in the same manner as described above, and
By using SYNDCL, calculations of equation (3) are performed, and S ₂ ' of 1/α ² to 1/α ⁶² and S 3 ' of 1/α ³ to 1/ _α ⁹³ can be calculated.

FIG. 4 is a block diagram showing the structure of the double error detection means 12. The double error detection means 12 has 31
The outputs of the 1/α calculation elements 43 connected in series, the 1/α ² calculation elements 44 connected in series, the outputs of the calculation elements 43 and 44 in each stage, and the output from the addition means 7 S ₀ ′ +
S ₁ '+S 2 ' is applied to the first-stage 1/α calculation element 43 _, and S ₂ '+S ₃ is applied to the first-stage 1/α ² calculation element ₄₄ . ' is applied. Here, the 1/α calculation element 43 is the element shown in FIG. 3b, and the 1/α ² calculation element 44 is the element shown in FIG. 3d. In addition, the coincidence detection circuit 45
As shown in FIG. 5, the E-OR gate 46 to which each bit of S ₀ '+S ₁ ' is applied and each bit output of the 1/α calculation element 43 is applied, and the E-OR gate 46 to which each bit of S ₀ '+S ₁ ' is applied, It consists of an E-OR gate 47 to which each bit is applied and each bit output of the 1/α ² arithmetic element 44 is applied, and a NOR gate 48 to which the outputs of the E-OR gates 46 and 47 are applied. ) is detected. That is, the output _a1 of the coincidence detection circuit 45 provided in the first stage is an output that becomes "1" when i-j=1, and the output a1 of the coincidence detection circuit 45 provided in the second stage is an output that becomes "1" when i-j=1.
The output a ₂ of No. 5 becomes "1" when i-j = 2, and similarly becomes "1" sequentially up to the output a ₃₁ of the 31st stage corresponding to the value of i-j. Therefore, the syndrome calculation means 3, 4, 5, and 6 calculate 1, α, α ² ,
Each time a division is executed by α ³ , the double error detection means 12 determines whether equation (8) holds true or not, and if there is a double error, the j-th division is performed. _{When the} result of
is obtained. Incidentally, the match value detection circuit 45' is i-j
=0, and outputs "1" when there is a single error.

FIG. 6 is a circuit diagram of the error calculation means 31,
By the ROM 49 inputting the detection outputs a ₁ to a ₃₁ from the double error detection means 12 and the output of the ROM 49,
From the lower bit of the 8-bit data of S ₀ ′+S ₁ ′, A,
B, C, ...G, H) are selectively added,
It is comprised of a selective addition circuit 50 that creates each bit E _i-0 to _{E i-7} (8 bits in total) of the error component E _i . As mentioned above, the error calculation means 31 calculates the formula (9), and in this case, 1+α ^ij can be converted to α ^x , and the ROM 49 converts 1+α ^ij to α ^x , and It determines the configuration of each bit of the result when 8-bit data is divided by α ^x . For example, when ij = 1, 1 + α is converted to α ²⁵ , and each bit of the error component E _i obtained by dividing S ₀ ′ + S ₁ ′ by α ²⁵ is E _i-7 = A + B + C + D + E + F + G + H E _{i -6} = A+B+C+D+E+F+G E _i-5 = A+B+C+D+E+F E _i-4 = A+B+C+D+E E _i-3 = E+F+G+H E _i-2 = A+B+C E _i-1 = C+D+E+F+G+H E _i-0 = B+C+D+E+F+G+H. Therefore, the selective addition circuit 50 that creates each of E _i-7 to _{E i-0} uses the AND gate 51 as follows:
Based on the signals output from the ROM49,
Select 8-bit data A to H of S ₀ ′+S ₁ ′, and select E-
The OR gate 52 performs modulo 2 addition. Therefore, even without performing actual division, the detection output a ₁ ~
By applying a ₃₁ , the error component E _i is obtained in real time.

Next, by the circuit shown in FIG. 1, C ₁ and C ₂
The error detection and correction operations will be briefly explained with reference to FIG.

As shown in Figure 7, the processing period for one frame is
Configure the timing of T ₁ to T ₆ and each of T ₁ to _{T 6}
Consists of 49 timings from t ₀ to t ₄₈ . C ₁ error detection and correction is performed at timings T ₁ to T ₃ , and C ₂
Error detection and correction are performed at timings _T4 to _T5 . First, the syndrome calculation means 3, 4, 5, 6 and the D-FF of each section are reset by the clear pulse CINT generated at _t0 of timing _T1 . This timing T ₁ is the timing at which the syndromes S 0 , S 1 , S 2 , and S ₃ are calculated by sequentially reading out the 32 symbols D ₃₁ to D ₀ stored in the RAM 1, and is the timing at which the syndromes S ₀ , S ₁ , S ₂ , and S ₃ are calculated _. The timing signals are distributed so that 32 timing signals SYRAM are generated. Therefore, the 32nd timing signal
When SYRAM occurs, syndrome S ₀ ,
S ₁ , S ₂ , and S ₃ have finished calculating. Next, the timing
_T2 is the timing for error detection, and is distributed so that 32 timing signals SYNDCL are generated. Also, the timing T ₂
The clear pulse SINT generated at timing _t0 generates the output of the AND gate 53 shown in FIG. 1, and the counter 16 is preset to "0". Therefore, every time the timing signal SYNDCL is generated, the counter 16 counts up and the syndrome calculation means 3, 4, 5, and 6 execute division by 1, α, ^α2 , and ^α3 once. , based on the results, single error detection and double error detection are performed. When 32 timing signals SYNDCL have been generated, if there is a single error or double error, one of the error positions j is held in the register 17, and the syndromes S ₀ , S ₁ , S ₂ , S ₃ j times by 1, α, α ² , α ³ is stored in the register 20, S _{0 ′} +S ₁ ′ is stored in the register 21, and the double error detection results a _{1 to 31} is held in the a register 13. Furthermore, the detection result of no error, single error, double error, or uncorrectability is indicated to the correction control means 23 and the uncorrectability determination means 22. Timing T ₃ is the timing to execute correction, and during timing T ₃ , the control signal is
The timing of selecting the error position i by SEL and reading out the symbol D _i at that address, and the adding means 3
The timing for writing the symbol D _i corrected in step 4 again to the same address in the RAM 1 is allocated, and the timing for reading and writing to correct the error position j is similarly provided. Therefore, at timing T ₃ , at timing T ₂ ,
The above processing is performed based on the data held in registers 13, 20 and 21, and correction is performed using the results.

In the case of _C2 error detection and correction, there are 28 symbols _D27 to _D0 . Therefore, at timing _T4 , there are 28 timing signals SYRAM for reading symbols _D27 to _D0 and calculating syndromes _S0 , _S1 , _S2 , and _S3 . The clear pulse SINT generated at timing _t0 clears all the data held during _C1 error detection and correction, and then the 28 timing signals SYRAM clear _the C2
The syndromes S ₀ , S ₁ , S ₂ , and S ₃ are obtained. Clear pulse at timing t ₀ at timing T ₅
When SINT occurs, the counter 16 is preset to "4" by the output of the AND gate 54 in FIG.

Here, the meaning of presetting "4" will be explained. As mentioned above, in RAM 1, there are data from the disk as follows: Address 0 1 2 3...30 31 Symbol D ₀ D ₁ D ₂ D ₃ ...D ₃₀ D ₃₁ Values of i, j 31 30 29 28...1 0 Addresses are assigned in the order of symbols read. However, as shown in equation (1), the exponent of α multiplied by the symbols D ₀ to D ₃₁ is
This is the opposite of the address, and the i and j determined by the circuit of FIG. 1 are the opposite of the actual address. Therefore,
As shown in FIG. 1, the actual address is obtained by inverting the 5-bit binary data representing i and j (2 ⁵ =32) using inverters 28 and 29. However, in case of _C2 error detection and correction, the symbols processed are at addresses 0 to 27
Since it is a symbol up to, the possible numerical values of i and j are 0 to 27. Therefore, if the numerical values of i and j are inverted as they are, the actual address will be shifted by "4", so "4" must be added before inversion. That is, an addition circuit for adding "4" is required, but if "4" is preset in the counter 16 that counts j, the addition circuit is unnecessary and the same circuit can be used.

After "4" is preset in the counter 16,
Timing signal generated during timing T ₅
There are 28 SYNDCL signals, and error detection for C ₂ is performed using this signal in exactly the same manner as at timing T ₂ described above. Then, at timing _T5 , error correction of _C2 is performed by the same operation as at timing _T3 .

(G) Effects of the Invention As described above, according to the present invention, the timing signals for reading symbols from the RAM and calculating the syndromes and the syndromes S ₀ , S ₁ , S ₂ , S ₃ are set to 1,
Since error detection can be realized by timing signals divided by α, α ² and α ³ , the number of timing signals required for calculation is reduced. Further, there is no need for a ROM for logarithmic conversion or the like for directly performing error detection calculations, which has the advantage of simplifying the circuit configuration and reducing the number of elements. Furthermore, it also has the advantage of increasing error detection speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a specific configuration of the syndrome calculation means shown in FIG. 1, and FIG. A circuit diagram showing ⁿ and 1/α ⁿ arithmetic elements, FIG. 4 is a specific block diagram of the double error detection means shown in FIG. 1, and FIG. 5 is a coincidence detection circuit shown in FIG. 4. 6 is a circuit diagram showing the configuration of the error calculation means, and FIG. 7 is a timing diagram showing the operation of the embodiment shown in FIG. 1. 1...RAM, 2...Data bus, 3, 4, 5, 6
...Syndrome calculating means, 7, 8, 9... Adding means, 10... Zero error detection means, 11... Single error detection means, 12... Double error detection means, 13... A register, 15... Counting means, 18... Latch pulse Generating means, 20, 21...Register, 22...Uncorrectable determination means, 23...Correction control means, 26...Encoder, 27...Error position calculation means, 30, 33...Multiplexer, 28, 29...Inverter, 31...Error calculation means .

Claims (1)

[Claims] 1. In a data error detection circuit that detects errors in data based on Reed-Solomon codes, data that is input in synchronization with a clock signal that controls syndrome calculation is Syndromes S ₀ , S ₁ , S ² , S ³ are calculated by repeatedly adding the results of multiplying the calculation results by 1, α, α ₂ , α ₃ (α is an 8th order primitive polynomial). At the same time, the calculated syndrome S ₀ ,
A syndrome calculation means that sequentially divides S ₁ , S ₂ , S ₃ by 1, α, α ² , α ³ and syndromes S ₀ , S ₁ , S ₂ , S ₃ output from the syndrome calculation means are all Based on the error zero detection means for detecting "0" and the division results S ₀ ′, S ₁ ′, S ₂ ′, and S ₃ ′ output from the syndrome calculation means for each division, Adding means for calculating S ₀ ′+S ₁ ′, S ₁ ′+S ₂ ′, S ₂ ′+S ₃ ′, and the above-mentioned S ₀ ′+S ₁ ′,
a single error detection means for detecting that S ₁ ′+S ₂ ′, S ₂ ′+S ₃ ′ are all “0”, and the above-mentioned S ₁ ′+S ₂ ′, S ₂ ′ outputted from the addition means +S ₃ ′ as α,
_The error _{position difference} ^a ₍ a ⁼ j _{- j} , ⁱ ，
j is an error position);
counting means for counting clock signals for controlling the division of the syndrome calculation means and holding a numerical value j indicating an error position based on the detection output of the single error detection means; error position calculation means for calculating i from a output from the double detection means; and output from the addition means when the detection output of the single error detection means is generated.
A data error detection circuit comprising: error calculation means for calculating an error component based on S ₀ ′+S ₁ ′ and the output a from the error position detection means.