Multiplexing of Interrupt and DMA Request Lines
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
This article describes a multiple card microprocessor system which allows multiple input/output (I/O) cards equal access to a fixed number of interrupt and direct memory access (DMA) resources. It allows each of the processors to select the requests to which it will respond without requiring unique wiring on each I/O card. In a multiple card microprocessor system, a typical problem is that of allocating processor resources (such as interrupt and DMA requests) for use by individual I/O cards. If a single set of resources is bussed across all cards, no two cards can request the same resource in order to avoid contention for it. That means that two of the same card type could not reside in the same system. Serial arbitration schemes have been used, but they can lock out the I/O cards at the end of the string.