Prioritized unidirectional distributed bus accessing system

TLDR: In this paper, a plurality of bus interface units (BIUs), capable of placing information packets on a unidirectional transmit bus, are coupled to the transmit bus at locations spaced there along.

Abstract: A plurality of bus interface units (BIUs), capable of placing information packets on a unidirectional transmit bus, are coupled to the transmit bus at locations spaced therealong. Each BIU comprises a transmit bus input port and a transmit bus output port, wherein the transmit bus input port of each BIU is coupled to the transmit bus output port of the next upstream BIU, and a receive bus input port connected to a receive bus. Each BIU includes a memory for storing at least one information packet to be transmitted and a control circuit associated with the memory. In a passive mode, the control circuit operates the BIU like a repeater, wherein packets received on its transmit bus input are reconstituted and retransmitted on its transmit bus output. In an active mode, the control circuit causes the BIU to transmit information packets stored in its memory. Each information packet may have a predetermined priority. The control circuit aborts transmission of an information packet whenever the BIU receives a higher or equal priority packet than it is transmitting and transmits the received packet in lieu of the aborted packet. Packets received during transmission, having lower priority than the packet being transmitted, are stored in memory for later transmission.