Patent ID: 6668266
Filing Date: 2003-12-23
Classification: G06F

Abstract:
A data processing device, comprising:a first processing unit; and a second processing unit whose operation is controlled by the first processing unit and including a register holding fixed-point data; an addition/subtraction circuit for processing fixed-point data; and a multiplication circuit for processing fixed-point data; first, second and third address buses through which addresses are transferred from the first processing unit; a first memory connected to the first and second addresses buses and not connected to the third address bus; a second memory connected to the first and third address buses and not connected to the second address bus; a first data bus connected to the first and second memories, the first and second processing units; a second data bus connected to the first memory and the second processing unit and not to the second memory; and a third data bus connected to the second memory and the second processing unit and not to the first memory; and wherein when a first instruction is executed to transfer data, whose bit length is shorter than the bit length of the register, from outside the second processing unit to the register, the second processing unit inputs the data justified to the higher-order side of the register and enters zero at a redundant lower-order side of the register, and wherein when second instruction is executed to transfer data, whose bit length is shorter than the bit length of the register, from outside the second processing unit to the register, the second processing unit inputs the data justified to the higher-order side of the register and enters zero at a redundant lower-order side of the register, and wherein when second instruction is executed to transfer data, whose bit length is shorter than the bit length of the register, from the register to the outside of the second processing unit, the second processing unit outputs a required bit length of the data from the higher-order side of the register to the outside.