Importance

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Abstract

To provide an external storage system using a semiconductor memory in which the data reading and writing between the host CPU can be processed faster than the conventional magnetic disk, and only a particular sector is not frequently written and erased so that the whole memory is effectively used over a long period of time. An address control scheme was introduced in which flexibility is given to the address relation between the host CPU and the external storage and the physical address of the semiconductor memory is not one-sidedly determined by the logical address possessed by the command of the host CPU. Command processing section 34 always prepares memory blocks and sectors for writing or erasing and copying in preparation for the command processing of the host CPU, and records and holds the correspondence relation between the physical address of the selected memory block 32i or sector and the command of the host CPU in address conversion table 36. The status of memory blocks and sectors is recorded in respective managing tables 35 and 60, and used for control of processings such as writing, erasing and copying in preparation for or in response to the command of the host CPU.

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First Claim