Asynchronous Arbiters

Abstract

When two or more processors attempt to simultaneously use a functional unit (memory, multiplier, etc.), an arbiter module must be employed to insure that processor requests are honored in sequence. The design of asynchronous arbiters is complicated because multiple input changes are allowed, and because inputs may change even if the circuit is not in a stable state. A practical arbiter and its implementation are presented. Implementation of various priority rules (linear, ring, mixed) is discussed, and building large arbiters with trees of two-user arbiters is considered.