BUS ARBITER WITH REINFORCED FUNCTION USING VARIABLE PRIORITY AND FAIRNESS

摘要

PROBLEM TO BE SOLVED: To change arbitration priority levels by making a bus arbiter include logic in which a fairness system is embedded. SOLUTION: When a plurality of devices simultaneously request a bus, this bus arbiter resets all the bits of a fairness register to zero and starts a fairness protocol sequence. The bus arbiter deasserts all currently asserted enabling signals. Then, the bus arbiter asserts an enabling signal to a request source which does not set 1 in a corresponding fairness register bit and has the highest priority. Subsequently, the bus arbiter uses fairness algorithm and asserts an enabling signal to a request source having the highest priority when there is another device to which a request signal is asserted and which sets 1 in a fairness bit.