EP0200124A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Decoding method and encoder-decoder for cyclic codes
Assignee: Hitachi Ltd
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Filing: 1986-04-18
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Granted: —
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Expires: 2006-04-18
Abstract
Abstract An encoder/decoder for detecting and correcting a burst error of a cyclic code uses a two-way feedback shift register including a chain of l pieces of flip flops and exclusive OR gates corresponding to generator polynomials. A received code word is provided to the two-way feedback shift register in a forward shift direction during a decoding mode. After inputting the received code word into the feedback shift register, if a syndrome is not equal to zero, the shifting direction of the feedback shift register is changed over, so that the shifting of the contents of the flip flops is repeated until a zero tester detects that outputs of selected ( l -m) pieces of the flip flops become all-zero. When the zezo tester detects the all-zero, the contents of remained m pieces of the flip flops are provided as an error pattern of the received code word.
Inventors
- 👤 Mari Horikawa
- 👤 Satoshi Kawamura
- 👤 Eisaku Saiki
- 👤 Syoichi Miyazawa
- 👤 Tsukasa Yamauchi
- 👤 Takeyuki Endo
- 👤 Kazuo Minorikawa
- 👤 Shoichiro Toyama
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 14:45
CPC Classifications
H; H03; H03M; H03M13/00; H03M13/03; H03M13/05; H03M13/13; H03M13/17; H03M7/00; H03K; H03K19/00
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
147 words
A decoding method for decoding a cyclic code by using a feed- back shift register which comprises ℓ, pieces of flip flops together with exclusive OR gates inserted into positions corresponding to a generator polynomial for the cyclic code, comprising: step for inputting a received code word to the feedback shift register in a forward shift direction, step for detecting a syndrome just after finishing to input said received code word, step for changing over a shifting direction of the feedback shift register when the syndrome is not equal to zero, step for repeating the shifting of the feedback shift register in the reverse direction until outputs of selected (ℓ-m) pieces of the flip flops become all-zero, and step for providing outputs of remained a pieces of the flip flops as an error pattern when said outputs of selected (1-m) pieces of the flip flops become all-zero.
Claim 2
Dependent Claim
147 words
A decoding method for decoding a cyclic code by using a feed- back shift register which comprises ℓ, pieces of flip flops together with exclusive OR gates inserted into positions corresponding to a generator polynomial for the cyclic code, comprising: step for inputting a received code word to the feedback shift register in a forward shift direction, step for detecting a syndrome just after finishing to input said received code word, step for changing over a shifting direction of the feedback shift register when the syndrome is not equal to zero, step for repeating the shifting of the feedback shift register in the reverse direction until outputs of selected (ℓ-m) pieces of the flip flops become all-zero, and step for providing outputs of remained a pieces of the flip flops as an error pattern when said outputs of selected (1-m) pieces of the flip flops become all-zero.
Claim 3
Dependent Claim
24 words
A decoding method according to claim 1, wherein said repeating step comprises step of detecting outputs of low-order (ℓ-m) pieces of the flip flops.
Claim 4
Dependent Claim
21 words
A decoding method according to claim 2, wherein said providing step provides outputs of high-order m pieces of the flip flops.
Claim 5
Dependent Claim
162 words
A decoder for decoding a cyclic code based on a generator polynomial having a degree 1, comprising: a two-way feedback shift register which includes a chain of 1 pieces of flip flops (1C~32C) , exclusive OR gates (73 N 77) inserted into positions of said chain corresponding to the generator polynomial and an input terminal (100) receiving a code word, a syndrome tester (34), to which all outputs of said flip flops are supplied, for detecting a syndrome of said received code word, a zero tester (36), to which outputs of selected (l-m)pieces of said flip flops are supplied, for detecting said outputs of the selected (1-m) pieces all-zero, an error pattern detecting means (35), to which outputs of remained m pieces of said flip flops are supplied, for detecting an error pattern of said received code word, and means (101) for changing over a shift direction of said two-way feedback shift register when said syndrome tester detects said syndrome not zero.
Claim 6
Dependent Claim
162 words
A decoder for decoding a cyclic code based on a generator polynomial having a degree 1, comprising: a two-way feedback shift register which includes a chain of 1 pieces of flip flops (1C~32C) , exclusive OR gates (73 N 77) inserted into positions of said chain corresponding to the generator polynomial and an input terminal (100) receiving a code word, a syndrome tester (34), to which all outputs of said flip flops are supplied, for detecting a syndrome of said received code word, a zero tester (36), to which outputs of selected (l-m)pieces of said flip flops are supplied, for detecting said outputs of the selected (1-m) pieces all-zero, an error pattern detecting means (35), to which outputs of remained m pieces of said flip flops are supplied, for detecting an error pattern of said received code word, and means (101) for changing over a shift direction of said two-way feedback shift register when said syndrome tester detects said syndrome not zero.
Claim 7
Dependent Claim
21 words
A decoder according to claim 4, wherein said zero tester receives outputs of low-order (1-m) pieces (1CN21C) of said flip flops.
Claim 8
Dependent Claim
25 words
A decoder according to claim 5 wherein said error pattern detecting means receives outputs of high-order m pieces (22C N 32C) of said flip flops.
Claim 9
Dependent Claim
43 words
A decoder according to claim 4, wherein said two-way feedback shift register further comprises alternative circuits (1d~32d) , each of which is attached to an input terminal of each of said flip flops and receives a control signal, from said change over means.
Claim 10
Dependent Claim
223 words
An encoder/decoder for a cyclic code based on a generator polynomial, comprising: two-way feedback shift register means which includes a chain of flip flops (1C~56C) and alternative circuits (1d N 56d) connected to inputs of said flip flops, exclusive OR gates (73-79) inserted into positions of said chain corresponding to several generator polynomials and input terminal (100) receiving a code word, a number of said flip flops coincides with the largest degree of said generator polynomials, means for selecting 1 pieces of said flip flops and said alternative circuits for constructing a two-way feedback shift register corresponding to the generator polynomial of said received code word, a syndrome tester (34), to which all outputs of said secected flip flops are supplied, for detecting a syndrome of said received code word, a zero tester (36), to which outputs of low-order (1-m) pieces of said selected flip flops are supplied, for detecting said outputs of said low-order (1-m) pieces, an error pattern detecting means (35), to which outputs of remained high-order m pieces (46C~56C) of said selected flip flops are supplied, for detecting an error pattern of said received code word, and means (101) for supplying a control signal to said alternative circuits for changing over a shift direction of said two-way feedback shift register when said syndrome tester detects said syndrome being not zero.
Claim 11
Dependent Claim
223 words
An encoder/decoder for a cyclic code based on a generator polynomial, comprising: two-way feedback shift register means which includes a chain of flip flops (1C~56C) and alternative circuits (1d N 56d) connected to inputs of said flip flops, exclusive OR gates (73-79) inserted into positions of said chain corresponding to several generator polynomials and input terminal (100) receiving a code word, a number of said flip flops coincides with the largest degree of said generator polynomials, means for selecting 1 pieces of said flip flops and said alternative circuits for constructing a two-way feedback shift register corresponding to the generator polynomial of said received code word, a syndrome tester (34), to which all outputs of said secected flip flops are supplied, for detecting a syndrome of said received code word, a zero tester (36), to which outputs of low-order (1-m) pieces of said selected flip flops are supplied, for detecting said outputs of said low-order (1-m) pieces, an error pattern detecting means (35), to which outputs of remained high-order m pieces (46C~56C) of said selected flip flops are supplied, for detecting an error pattern of said received code word, and means (101) for supplying a control signal to said alternative circuits for changing over a shift direction of said two-way feedback shift register when said syndrome tester detects said syndrome being not zero.
Claim 12
Dependent Claim
15 words
An encoder/decoder according to claim 8, wherein said number of said flip flops in 56.
Claim 13
Dependent Claim
16 words
An encoder/decoder according to claim 9, wherein said 1 pieces are 32 pieces or 56 pieces.
Claim 14
Dependent Claim
34 words
An encoder/decoder according to claim 10, wherein said selecting means comprises a selecting circuit (71,72) inserted between the 24th flip flop from said input terminal and the 25th flip flop from said input terminal.
References Cited (Backward Citations)
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