Error data correcting system

Claim 1

An error data correcting system in which a series of n data words W 1 through W n each including m bits has associated therewith a P check code ##EQU24## and a Q check code ##EQU25## the system for correcting erroneous data words W c , and W d , to produce correct data words W c and W d (l≦c<d≦n), the system generating a first syndrome value ##EQU26## and a second syndrome value ##EQU27## when the series of data words includes erroneous data words W c' , and W d' , respectively, the system comprising: a first input terminal for receiving said series of data words and said associated first and second syndrome values; an auxiliary matrix circuit for multiplying said first syndrome value by an auxiliary matrix T - (n+1) ; a T matrix operation circuit for receiving the output of said auxiliary matrix circuit and for shifting said received value c positions to output T c- (n+1) S 2 ; a P register coupled to said first input terminal for receiving said first syndrome value; switch means for selectively coupling the output of said P register to the input of said T matrix operation circuit to cause said T matrix operation circuit to store S 1 +T c- (n+1) S 2 ; a second input terminal for receiving an error data pointer; an error word control circuit coupled to said second input terminal for generating an interval signal k=d-c corresponding to the series positional difference between said second error word W d' and said first error word W c' in response to said error data pointer; a first gate circuit coupled to the output of said T matrix operation circuit; a matrix generating circuit for receiving said interval signal k from said error word control circuit, for generating a matrix signal corresponding to a specific bit in the output of said T matrix operation circuit, and for supplying said matrix signal to said first gate circuit, said first gate circuit for combining said output of said T matrix operation circuit (T c- (n+1) S 2 with said matrix signal k to generate a second corrected data word W de ; a first buffer for storing said second corrected data word W de ; a second buffer coupled to said P register for receiving and storing said first syndrome value S 1 ; and means coupled to said first buffer for receiving said second corrected data word W de and to said second buffer for receiving said first syndrome value S 1 and for combining said second corrected data word W de and said first syndrome value S 1 to generate a first corrected data word W ce .