Abstract: A device operable as an interface controller for a defined data bus, wherein the interface controller operates to transfer entire blocks of data, bidirectionally, one byte at a time, while making each byte available as it is received for use by either the computer or by the memory. In addition, the present invention utilizes an interface controller with a single flow-through register, and pluralities of switches, operable in accordance with decoded commands for transferring data in the aforementioned manner in either direction through the same register.