Method and apparatus for determining address location and taking one of two actions depending on the type of read/write data transfer required

摘要

A bus interface unit for passing data between an I/O bus and a system bus in a dual bus computer system is provided. The bus interface unit has incorporated therein an address listing and compare function to determine whether a requesting device on the I/O bus is to read data from or write data to an address on the system bus. If so, the bus interface unit allows passing of the data therethrough. If not, the system bus is relinquished and the requesting device writes to the address on the I/O bus. Also, compare logic is incorporated in the bus interface unit which decodes system bus addresses originated from a system bus controller such as the DMA, to determine whether the destination of the transfer is to system memory or the I/O bus.