REFRESHING METHOD OF MEMORY DEVICE

摘要

PURPOSE:To prevent competition between an access time of memory by a master device and a refreshing operation period, to perform refreshing operation securely and to improve the utilization efficiency of a system by adding a circuit which enters the refreshing operation synchronously with the access by the master device. CONSTITUTION:A refreshing timing control mode selector 10 consists of a refreshing timing controller 10a which generates the starting timing of refreshing operation and a mode selecting circuit 10b which selects the mode of the starting of refreshing operation synchronizing with the access by the master device 1 or mode of the asynchronous starting. Then, 11 is a refreshment request device which makes requests by modes of the refreshment corresponding to respective modes and 12 is a memory timing generator which includes the timing of RAS only refreshment. The timing for outputting RAS for refreshment is set in the mode of the starting synchronizing with the access by the master device 1 to start the refreshing operation securely at certain specified timing when the memory is not accessed.