Coding and decoding method

• US 4,897,839 A
• Filed: 02/05/1988
• Issued: 01/30/1990
• Est. Priority Date: 03/25/1987
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Oda, Yoshiaki, Nishijima, Toshihisa, Inoue, Tohru, Yoshida, Hideo, Yamagishi, Atsuhiro
• Primary Examiner(s): ATKINSON, CHARLES
• Application Number:
  US07/152,550
• Time in Patent Office: 725 Days
• Field of Search: 371/37, 371/38, 371/39, 371/40, 371/57
• US Class Current: 714/785
• CPC Class Codes: H03M 13/15 Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] codes H03M13/17 takes precedence

Abstract

Disclosed is a coding and decoding method, in which a certain promised nonzero symbol is appended for coding and decoding, thereby disallowing the presence of a codeword with all-"0" data after coding. The method enables the detection of a fault in an external circuitry by checking the occurrence of an all-"0" received word attributable to the external circuitry.

Claims

1. A coding and decoding method, comprising the steps of:

calculating syndromes for a string of information symbols utilizing a nonzero constant in the syndrome calculation;

computing check symbols for each of the calculated syndromes;

transmitting a code word containing said information symbols and said check symbols;

receiving a transmitted code word;

calculating syndromes for said received code word utilizing a nonzero constant in the syndrome calculation;

determining the existence of an uncorrectable error in said received word when said nonzero constant is appended to a calculated syndrome at a predetermined position;

determining the existence of a correctable error in said received word when said nonzero constant is appended to a calculated syndrome at other than said predetermined position; and

determining the absence of error in said received word when the calculated syndromes are all zero.

3. A coding and decoding method according to claim 1, wherein when the syndromes are calculated, a syndrome calculating register is used to implement a syndrome calculation starting at a nonzero state of said syndrome calculating register.

2. In a coding and decoding method utilizing the calculation of syndromes based on information symbols, the improvement comprising:

determining the existence of a code word containing all "0" information symbols; and

appending a certain nonzero constant to said code word containing all "0" information symbols such that a check symbol section does not become "0".