| 摘要 |
PURPOSE:To calculate a variation range of the input signals with high accuracy and with no fear of overflow even with the signals out of said variation range, by providing a barrel shifter, an overflow detector and an overflow corrector to a multiplying circuit having its variation range of input signals fixed between -1 and +1. CONSTITUTION:A multiplier 5 delivers the value of (2N-1) bits as a product and a barrel shifter 6 shifts the output of a multiplier 5 in the upper direction by an amount equivalent to the value (K+L) given from an input terminal 7 for shift amount. Then the shifter 6 delivers N bits between the (K+L+1)-th bit and the (K+L+N+1)-th bit of the input given to the shifter 6. An overflow detector 10 checks the upper (K+L+1) bits of the output of the multiplier 5 and decides the generation of an overflow when all bits have no equal value. Therefore an instruction is given to a selection circuit 11 so that the negative maximum value given from an input terminal 9 for negative maximum value with the highest bit of the multiplier 5 set at '1' and that the positive maximum value given from an input terminal 8 for positive maximum value is delivered through an output terminal 12 when said highest bit is set at '0', respectively. |
