| 摘要 |
PROBLEM TO BE SOLVED: To shorten the executing time of the calculation of (1+a)×b by using two source data. SOLUTION: A data processor respectively reads 32-bit data respectively containing 16-bit fixed-point data (a) and (b) from registers 122 and 123 which are designated by an instruction requesting the execution of the calculation of (1+a)×b and supplies the data (a) and (b) to a multiplier 130 by means of multiplexers 117 and 118 and the 32-bit data to an adder 132 through a one- bit left shifter 131 for adjusting the position of base point. The processor adds 16-bit '0' to the lower-rank side of the data (b) by means of a shifter 133 and supplies the obtained 32-bit data to the adder 132 through a selector 134. The adder 132 obtains the result data of the above-mentioned calculation. The result data are written in a register designated by the above instruction. The above calculation by means of the adder 132 and multiplier 130 is executed in one machine cycle. This arithmetic unit can execute the product-sum operation of a×b+c and multiplication of a×b by switching the operations of the selector 134. |
