Abstract: A direct memory access control apparatus performs direct data transfer between a memory and an input/output controller in a data processing system. When the system is placed in a direct memory access mode upon receipt of a direct memory access request from the input/output controller, a data bus connected between the input/output controller and the memory is separated from a central processing unit by means of a data bus separating circuit, and an address bus of the memory is also separated from the central processing unit by means of an address bus switch circuit. The address bus of the memory is connected to a direct memory access controller by means of the address bus switch circuit. Therefore, the memory is addressed by the direct memory access controller through the address bus while the data is directly transferred between the memory and the input/output device through the data bus.