PROBLEM TO BE SOLVED: To prevent influence of the potential fluctuation to an outside element whose access frequency is high on an outside element whose access frequency is low, to prevent the increase of current consumption, and to prevent the influence of spurious radiating noise to the outside element whose access frequency is low. ;SOLUTION: In this bus control microcomputer, two system outside buses 14 and 15 are connected with two sets of ports 12 and 13, and a flash memory 3 whose access frequency from a microcomputer 11 is high is connected with the outside bus 14, and an SRAM(static RAM) 4 and a G/A(gate array) 5 whose access frequency from the microcomputer 11 is low are connected with the outside bus 15. Moreover, access is performed only to one outside bus among the two system outside buses 14 and 15 according to a chip select signal, and even when the potential of a data bus 18 whose access frequency is high fluctuates, any influence on a data bus 22 whose access frequency is low can be prevented, and the increase of current consumption can be prevented.;COPYRIGHT: (C)1999,JPO
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