Data storage apparatus for efficient utilization of limited cycle memory material

Abstract

In the semiconductor memory device relating to the present invention, the memory is divided into a plurality of blocks having a plurality of sectors and stores user data in units of sectors. When writing one sector of user data, the controller converts the logical block address to a physical block address using the address table. The controller selects one unused block and writes one sector of user data to this unused block. When user data are stored in this unused block, all data in this block are deleted before data are written thereto. Next, the controller reads data corresponding to other sectors from a block corresponding to the physical block address discussed above and copies this data in order to an unused block. When the writing ends, the control portion overwrites the address table so that the physical address of this unused block is assigned to the logical block address discussed above. In other words, in the semiconductor memory device relating to the present invention, a new storage location is selected from the unused blocks when user data are overwritten, data are written to one sector of this new storage location, and data in other sectors are copied from the old storage location. Consequently, a buffer for temporarily handling data which are not to be overwritten is unnecessary.