Patent ID: 6341297
Filing Date: 2002-01-22
Classification: H03M

Abstract:
A Galois field substitution circuit of a Galois field of ap, in a syndrome polynomial calculating circuit, comprising:j Galois field multiplication circuits; an exclusive OR circuit having (j+1) inputs; a D-flipflop; a selector circuit; and a counter circuit; wherein (a) j blocks of time divisionally multiplexed signals are entered as input signals, of which first one block signal is entered to a first input of said exclusive OR circuit, with second to jth block signals being entered to first to (jâˆ’1)th Galois field multiplication circuits, respectively; (b) outputs of said first to (jâˆ’1)th Galois field multiplication circuits are fed to second to jth inputs of said exclusive OR circuit; (c) an output of said exclusive OR circuit is fed to a data input terminal of a D-flipflop; (d) an output of said D-flipflop is branched into two, one of which is fed to the jth multiplication circuit and the other of which is entered to a first input of said selector circuit; (e) an output of said jth Galois field multiplication circuit is fed to a (j+1)th input of said exclusive OR circuit; (f) input clock signals are fed to a clock terminal of said D flipflop and to said counter; (g) a control signal output by said counter is entered to said selector circuit as a selection control signal; (h) said counter counts a one-frame signal input and sets the control signal to logical 1 to output the logical 1 signal when the counter value is that at the last inputting of the one-frame signal; (i) said selector circuit selectively outputs a signal at a second input and a signal at a first input if the selection control signal is the logical 0 or logical 1, respectively, while the second input terminal of said selector is normally fixed at the logical 0; and (j) an output of the D flipflop and the counter value are reset after inputting of a one-frame input, and wherein (k) the Galois field multiplication circuits have each a Galois field a with power of p to jp.