| 摘要 |
PURPOSE:To accelerate the operation of the entire burrel shifter by selecting and outputting a sign bit by a sign look-ahead circuit in the case of performing left arithmetic shift to the data of an N/2 bit width. CONSTITUTION:In half width data shift, the data 10-131 of 32 bits are inputted to an input butter 47, amplified and then simultaneously supplied to the sign look-ahead circuit 46 and a 7-bit shifter 48. To the sign look-ahead circuit 46, shift amount control signals SA0-SA4 and shift type control signals are inputted. When the shift type is the left arithmetic shift, the one to be a most significant bit on a low-order side after the shift is selected from the input data 10-131 as the sign bit and the value of the sign bit is outputted to a sign expansion line 51. In parallel to the operation in the sign look-ahead circuit 46, the input data 10-163 are inputted to the 7-bit shifter 48. The 7-bit shifter 48 is driven and operated by a 7-bit shifter control circuit 45 and the data S0-S63 are outputted. |
