High speed barrel shifter
AssigneeConcurrent Computer Corporation
InventorsJames E. Hodge, Kenneth C. Yeager
Life of this patent
Estimating the term…
Abstract
A multi-function high speed barrel shifter comprising three functional levels. The first level performs 1/4 word shifts by a selectable amount. The second level performs 1/8 word shifts on the portion of the word to be shifted and, where desired, fills the remainder of its output with fill bits. The third level performs 1/32 of a data word shift. All shifting and filling are controlled by an input control signal which specifies the operation, direction and shift amount. The circuit is easily complimented in LSI Technology and is easily cascaded to double the size of the data word handled thereby.
Claims13
A barrel shifter responsive to control signals for producing a plurality of operations on a plurality of data bits including rotate, logical shift, arithmetic shift, rotate with programmable fill, logical shift with programmable fill, arithmetic shift with programmable fill, rotate and mask and extract and mask, the shifter comprising, in combination:
- a first level of logic circuits responsive to the data bits for producing at its output the data bits rotated by a selectable number of either 0, 8, 16, or 24 bit positions as defined by said control signals;
- a second level of logic circuits coupled to the output of said first level of logic circuits for producing at its output the data bits from said first level of logic circuits shifted by a selectable amount of 0 or 4 bit positions as defined by said control signals, said second level logic circuits including means responsive to said control signals to replace selectable data bits of the output data bits therefrom with selectable fill bits in accordance with the operation selected by said control signals;
- and
- a third level of logic circuits coupled to the output of said second level logic circuits for producing at its output in response to said control signals data bits shifted by a selectable bit amount of 0, 1, 2 or 3 bit positions.
A barrel shifter responsive to control signals for producing a plurality of operations on a plurality of data bits organized in bytes of 8 data bits each including rotate, logical shift, arithmetic shift, rotate with programmable fill, logical shift with programmable fill, arithmetic shift with programmable fill, rotate and mask and extract and mask, the shifter comprising, in combination:
- an even and an odd barrel shifter, each comprising:
- a first level of logic circuits responsive to the data bits for producing at its output the data bits rotated by a selectable number of half-words of either 0, 1, 2 or 3 half-words as defined by said control signals;
- a second level of logic circuits coupled to the output of said first level of logic circuits for producing at its output the data bits from said first level of logic circuits shifted by a selectable number of bytes, either 0 or 1 as defined by said control signals, said second level logic circuits including means responsive to said control signals to replace selectable data bits of the output data bits therefrom with selectable fill bits in accordance with the operation selected by said control signals;
- a third level of logic circuits coupled to the output of said second level logic circuits for producing at its output, in response to said control signals data bits shifted by a selectable bit amount of 0, 2, 4 or 6 bit positions;
- said even shifter being coupled to receive even numbered data bit positions at its input to its said first level of logic circuits;
- said odd shifter being coupled to receive odd numbered data bit positions at its input to its said first level of logic circuits;
- and
- a plurality of 2:1 output multiplexers each coupled to the same designated position of the third level logic circuit from said odd shifter and from said even shifter to produce in response to control signals thereto either a 0 or a 1 bit shift of the output from said odd shifter and said even shifter in accordance with the control signals applied thereto.
Dependencies are inferred from the claim text.