Multiplexed communication protocol between central and distributed

Abstract

A multiplexed communication protocol for broadcasting interrupt, DMA and other miscellaneous data across a bus from a central peripheral device to a plurality of distributed peripheral devices associated with each processor in a multiprocessor computer system. The multiplexed bus includes a data portion and a status portion, where the status portion indicates one of several different cycle types executed on the bus, and where each cycle type further indicates the data asserted on the data portion. The cycle types further include address and data read and write cycles to allow access of the registers in the distributed devices via the multiplexed bus. Thus, system interrupt, address, data, DMA, NMI and miscellaneous cycles are defined where a system interrupt cycle is continually executed on consecutive cycles until interrupted by a request to execute another cycle type. The cycle sequence is implemented to insert system interrupt cycles between the address and data cycles to prevent significant channel latency when system interrupts occur.