Patent ID: 8108334

Claim:
A search method, performed by a tangible search circuit in a decoding unit of low-density parity check codes, used for searching a minimum value and a next minimum value from r input values, where r is an integer greater than 3, comprising: performing operations on two input values V 1 , V 2 of the r input values, comprising: comparing the two input values V 1 and V 2 ; determining the input value V 1 as a smaller value Wm and the input value V 2 as a greater value Lm, if the input value V 1 is smaller than the input value V 2 ; and determining the input value V 2 as the smaller value Wm and the input value V 1 as the greater value Lm, if the input value V 2 is smaller than the input value V 1 ; performing operations on two input values V 3 , V 4 of the r input values, comprising: comparing the two input values V 3 and V 4 ; determining the input value V 3 as a smaller value Wn and the input value V 4 as a greater value Ln, if the input value V 3 is smaller than the input value V 4 ; and determining the input value V 4 as the smaller value Wn and the input value V 3 as the greater value Ln, if the input value V 4 is smaller than the input value V 3 ; performing operations according to the smaller value Wm, the smaller value Wn, the greater value Lm, and the greater value Ln, comprising: generating a first comparison signal that indicates the smaller of the smaller value Wm and the smaller value Wn; selecting one of the greater value Lm and the smaller value Wm as a compared value Wp in a first multiplexing circuit according to the first comparison signal; selecting one of the greater value Ln and the smaller value Wn as a compared value Wq in a second multiplexing circuit according to the first comparison signal; generating a second comparison signal that indicates the smaller of the compared value Wp and the compared value Wq; selecting one of the compared value Wp and the compared value Wq as a greater value Lo in a third multiplexing circuit according to the second comparison signal; and selecting one of the smaller value Wm and the smaller value Wn as a smaller value Wo in a fourth multiplexing circuit according to the first comparison signal; and producing the minimum value and the next minimum value according to the smaller value Wo and the greater value Lo.