Multiplexed interrupt/DMA request arbitration apparatus and method

In an arbitration apparatus and technique, the request lines from a plurality of potential requestors serve both as interrupt and DMA bus request signal lines to an arbitration device. The arbitration device selects among contending requestors on a priority basis and generates a grant signal interpreted by the requesting devices either as an interrupt grant or a bus grant depending upon whether or not an interrupt acknowledge signal is received. This effectively multiplexes the grant request lines from a plurality of requestors to greatly reduce interconnection complexity and cost. A single interrupt grant/bus grant multi-wire signal cable connects from the arbitration device to the individual requestors. A grant will appear on a single line thereof connected to an individual requestor that has been granted either an interrupt or access to the bus. Interrupt requests from the requestors are ORed together and simultaneously presented to a central controlling microprocessor. The arbitration device determines which requestor will be granted access and, under control of the central control microprocessor, the arbitrator gates an interrupt grant or a DMA grant signal to the device selected by the arbitration mechanism. The dual usage of the grant and request lines by the arbitration device represents a multiplexing feature to further reduce interconnections.