Patent ID: 6574683
Filing Date: 2003-06-03
Classification: G06F

Abstract:
An external direct memory access unit comprising:an event recognizer adapted to recognize one external event of a plurality of event types, said event recognizer including an event register including a bit corresponding to each event type set upon receipt of an external event of said corresponding type; a priority encoder connected to said event recognizer selecting for service one recognized external event based upon priority assigned to each event type, said priority encoder resetting said corresponding bit of said event register upon selection of an external event; a parameter memory storing direct memory access request parameters corresponding to each event type at corresponding addresses, each of said direct memory access request parameters stored in said parameter memory include a priority for centralized transaction processor independent of said priority of said event recognizer for said corresponding event type; and an external direct memory access controller connected to said priority encoder and said parameter memory recalling service request parameters from said predetermined address in said parameter memory corresponding to said recognized event and submitting said recalled direct memory access request parameters to a centralized direct memory access unit, said centralized direct memory access unit including a request queue for each of a plurality of priority levels storing received and not yet executing direct memory access requests, said centralized direct memory access unit returning a queue acknowledge signal to said external direct memory access controller upon acceptance of a direct memory access request and a stall signal if said request queue of the corresponding priority level is full.