BUS CONTROLLER FOR INPUT AND OUTPUT DEVICE

PURPOSE:To form a bus controller having the minimum composition all the time by appropriately combining packages according to the difference in the number of input and output devices and in an access system. CONSTITUTION:A bus controller 1 is composed of the functional blocks of a high-order bus interface part 2, a high-order/low-order (IO) bus converting part 3, and an IO bus interface part 7 which never depend on the difference in the number of input and output devices 13 and in the access modes of the devices 13 and the functional blocks of a fault editing part 4, a DMA alarm notifying part 5, and a competitive circuit part 6 which depend on the difference in the number of the devices 13 and in the access modes of the devices 13. Further, the controller 1 has physical composition composed of a package 8 to house the high-order bus interface part 2, the high-order/low-order bus converting part 3, and the IO bus interface part 7 and packages 9, 10 and 11, in which the dependent functions are combined so that their attributes and hardware quantity can be in the optimum states. Thus, the bus controller can be composed by combining the packages suitable for the attributes according to the difference in the number of the subordinate input and output devices and in the access modes.