| 摘要 |
PURPOSE:To realize the change of allocation of positive and negative numbers against left and right shifts by outputting an extra bit compared with the desired output data width via a right 2<n-1>-bit shifter set at the final stage and then using said extra bit. CONSTITUTION:A multiplexer 71 serving as a right 8-bit shifter 7 contains an extra bit compared with the input data width. This extra bit is used to secure correspondence to the right 8-bit - left 7-bit shifts and numbers -8-7 respectively. Then a shift number 102 with which the right and left shifts are allocated to the negative numbers respectively is supplied for the actuation of a shift circuit 100. An inverting circuit 101 which inverts the shift number at every bit is added to the circuit 100. Thus the circuit 100 where the allocation of negative and positive numbers are reversed against the right and left shifts is obtained with the use of an extremely simple means that shifts the output result to the right by one bit. |
