Memory refreshing system having selective execution of self and normal refresh operations for a plurality of memory banks

Abstract

A memory refreshing system that can dynamically execute a self-refresh operation, even though the computer system is in a normal operational mode and can thus save the power consumption, and includes a memory refreshing system, for a memory system including a plurality of memory banks, which comprises a memory refreshing device, provided in each of the memory banks, for performing a refresh operation within a corresponding memory bank by, e.g., units of rows in response to a refresh request; a first memory refresh controller for supplying a refresh request to the memory system every first time period; a second memory refresh controller, provided for each of the memory banks, for supplying a refresh request to the corresponding memory bank every second time period that is longer than the first time period; a memory access monitor, provided for each of the memory banks, for detecting an access to the corresponding memory bank; a timer, provided for each of the memory banks, for generating a timer output when a first predetermined time has elapsed since a last access to the corresponding memory bank, and for canceling a counted timer value in response to the next access to the corresponding memory bank; and a selector, provided for each of the memory banks, for selecting one of the refresh requests from the first and the second memory refresh control means in accordance with the timer output.

Dependencies are inferred from the claim text.