An arbitration unit with circular or 'round-robin' priority, particularly for multiprocessor systems with synchronous symmetrical processors

摘要

In a synchronous arbitration unit with circular (round-robin) priority for arbitrating between N requests (Ri) for access to common resources of a multiprocessor system, the requests (Ri) stabilized in an input register (40) timed by a clock signal (CLK1) are applied as inputs to a fixed-priority arbitration network (44) having 2N-1 inputs, N-1 of the requests being applied both to a first set of N-1 lower-priority inputs of the network and, through masking circuits (42) which selectively mask the requests with a binary masking configuration generated by mask-generating circuits (43) in accordance with predetermined priority-rotation criteria, to a second set of N-1 higher-priority inputs of the network, in the same order of input priority. The grant signals output by the network are latched in an output register (41) after logical OR of the grant signals associated with the same request and the arbitration unit thus formed has a minimal arbitration time and is constituted by a small number of logic components.