Barrel shifter including rotate operation

Claim 1

A barrel shifter comprising: (a) shifting means for selectively shifting an N-bit input data by a given shift count in response to a plurality of shift signals indicative of a shift count in combination and outputting a 2N-bit output data; (b) ANDing means connected to said shifting means for ANDing a carry signal and a carry rotate signal to insert a carry bit behind a least significant bit position of the shifted N-bit output in cooperation with the shift signals; (c) ORing means connected to said shifting means for finding logical sums of each of N lower significant bits of the same in response to a rotate signal to obtain an N-bit rotated data without carry and logical sums of each of N lower significant bits of the 2N-bit output data and each of (N-1) higher significant bits of the same in response to a carry rotate signal to obtain an N-bit rotated data with carry; and (d) calculating means connected to said shifting means for calculating an actual shift count in accordance with a formula of x-(N+1)(i)(i=0, 1, 2, . . . where x denotes a rotate count and N denotes an input data bit length, when the rotate count x is more than the input data bit length N, and for outputting the calculated shift signals to said shifting means to rotate the N-bit data with carry by a rotate count more than the input data bit length N.

Claim 8

A method of rotating an input data with a bit length of 8 or 16 bits together with a carry bit by a rotate count more than 8 or 16 bits in a 32-bit barrel shifter, wherein an actual rotate count is determined by calculating a remainder of a division x/N+1, where x denotes a rotate count and N denotes an input data bit length, in accordance with the following steps of: (a) finding an AND product of a carry rotate signal, an 8-bit byte signal and 9 to 17 bit rotate count signals to generate a subtract signal SB 1 indicative of a subtrahend of (-9); (b) finding an AND product of the carry rotate signal, the 8-bit byte signal and 18 to 26 bit rotate count signals to generate a subtract signal SB 2 indicative of a subtrahend of (-18); (c) finding an AND product of the carry rotate signal, the 8-bit byte signal and 27 to 31 bit rotate count signals to generate a subtract signal SB 3 indicative of a subtrahend of (-27); (d) finding an AND product of the carry rotate signal, a 16-bit word signal and 17 to 31 bit rotate count signals to generate a subtract signal SW 1 indicative of a subtrahend of (-17); and (e) subtracting a subtrahend indicated by the subtract signals SB 1 , SB 2 , and SB 3 , from a 9 to 31 bit rotate count and a subtrahend indicated by the subtract signal SW 1 from a 17 to 31 bit rotate count to obtain the actual rotate count.

Claim 9

A method of rotating an input data with a bit length of 8 or 16 bits together with a carry bit by a rotate count more than 8 or 16 bits in a 32-bit barrel shifter, wherein an actual rotate count is determined by calculating a remainder of a division x/N+1, where x denotes a rotate count and N denotes an input data bit length, in accordance with the following steps of: (a) finding an AND product of a carry rotate signal, an 8-bit byte signal and 9 to 17 bit rotate count signals to generate a subtract signal SB 1 indicative of a subtrahend of (-9); (b) finding an AND product of the carry rotate signal, the 8-bit byte signal and 18 to 26 bit rotate count signals to generate a subtract signal SB 2 indicative of a subtrahend of (-18); (c) finding an AND product of the carry rotate signal, the 8-bit byte signal and 27 to 31 bit rotate count signals to generate a subtract signal SB 3 indicative of a subtrahend of (-27); (d) finding an AND product of the carry rotate signal, a 16-bit word signal and 17 to 31 bit rotate count signals to generate a subtract signal SW 1 indicative of a subtrahend of (-17); and (e) subtracting a subtrahend indicated by the subtract signals SB 1 , SB 2 , and SB 3 , from a 9 to 31 bit rotate count and a subtrahend indicated by the subtract signal SW 1 from a 17 to 31 bit rotate count to obtain the actual rotate count.