PURPOSE: To obtain a microprocessor having high performance without increasing the chip size by sharing an arithmetic executing part with a microprocessor and a DMA controller and applying a microprogram system as a control system for both said microprocessor and controller for unification of a microprogram ROM.

CONSTITUTION: The part enclosed by a chain line is formed on a semiconductor chip and an arithmetic execution part 2 is used in common by a CPU and a DMA controller. An ALU 3, a counter 4 and a bus interface circuit 5 are also shared within the part 2. In other words, each operation is carried out by using the same ALU 3 and counter 4 in a time division system. Then the address and data signals are transferred with an internal bus 6 through the common circuit 5. In addition, a microprogram control system with which the logic design and its change are easy is applied. While the control part of the CPU is unified with the control part of the DMA controller. This improves the operating efficiency of a data processor.