A processor for use in a digital data processing system includes a bus interface circuit for transferring data to and from other units in the system and for controlling the transfer of information within the processor over an internal bus. The bus interface circuit includes two state machines, one for controlling the internal transfers of information, and the other for controlling the external transfers of information. The state machines communicate through flags which indicate when external operations are pending. A plurality of latches are provided to receive write data, a write address and a read address from other portions of the processor, and an input latch receives signals from other units in the system, thereby allowing both a wire operation and a read operation to be initiated at the same time. The processor continues operating unless another operation is required.