PURPOSE: To attain the DMA control even in case plural input/output devices are connected to a channel by setting the flag information to a desired input/output device column belonging to a desired channel provided to a control table and then updating said flag information.

CONSTITUTION: A processing part 5 of a processor 1 sets the information 1 to a column F1 of a control table 4 and then sends an enable signal E to an input/ output device I1. A DMA control part D1 performs the writing/reading of data to a memory 6 through the device I1. When this access is over, the part D1 sends an end signal G to the processor 1. The part 5 refers to a time control part 2 to discriminate that the signal G is delivered from the device I1. Then the part 5 updates the information of the column F1 and then transmits again the signal E to an input device I2.