Microprocessor, which cooperates with a coprocessor

摘要

PURPOSE:To suppress the occurrence of a bus-neck state by separating data transfer to a coprocessor from a system bus. CONSTITUTION:A 32-bit microprocessor 100 is connected to a memory 120 through a bus control unit 101, the data bus D of 32-bit width, and the address bus A of 32-bit width. Besides, the coprocessor (FPU) 110 for floating point operation is connected to the CPU 100 through a slave processor bus control unit 104, the data bus CD of 32-bit width and the address bus CA of 9-bit width. Then, the data transfer with the coprocessor FPU 110 is executed by using the exclusive data bus CD and the exclusive address bus apart from the data bus D and the address bus A for accessing the memory 120. Thus, the duty cycle of the system bus at the time of the execution of an instruction to be expanded by the coprocessor can be reduced, and the occurrence of the bus neck can be suppressed.