Method and apparatus for local memory and system bus refreshing with single-port memory controller and rotating arbitration priority

摘要

According to the invention, roughly described, the EISA arbitration scheme is used for arbitrating among a plurality of requestors for a system bus, the requestors including the CPU, a refresh controller, EISA devices and ISA/DMA devices. A refresh control signal is asserted if the refresh controller wins the arbitration, and a CAS# before RAS# refresh is performed on local memory in response to the refresh control signal after completion of any CPU access to local memory then taking place. The CPU can continue to access external cache during system bus refresh, and a CPU access to local DRAM is delayed only by the amount of time required for the shorter local DRAM refresh to complete.