Computer interrupt cct with automatic priority modification - allows low priority input after predetermined number of top priority inputs

摘要

Low priority inputs are serviced in the normal sequence until delayed by repeated service requests on the top priority port. When a low priority signal is received and not immediately acted upon a counter associated with its input starts to record the number of top priority interrupts. If this number exceeds a pre-determined figure the sequence is changed and the waiting signal is given top priority. The system is designed to ensure that top priority users obtain preferential treatment but without completely neglecting low priority users when several top priority users are at work.