| 摘要 |
A product-sum operating device with a rounding function for executing a product-sum operation of 16 bits considering the place of the addend in a register. Selective input/expansion means of the product-sum operating device expands data at 31st to 16-th bits of a 40-bit register (1) if a control signal (Position) from the outside takes on "1", and data at 15-th to 0-th bits of the 40-bit register if the control signal (Position) takes on "0", to 40-bit data and transfers the expanded data to the product-sum operating device. This product-sum operating device executes a product-sum operation using 40-bit data, and a multiplicand B and a multiplier C both of 16-bit data. Rounding/selective output means (43) rounds the 40-bit data into 16-bit data if a control signal (Round) from the outside takes on "1", and outputs the rounded data to the place of the addend in the 40-bit register specified by the control signal (Position).
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