Data security device for storing data at a peripheral part of the device during power down thus preventing improper retrieval

摘要

A memory system having an erasable programmable read only memory (EPROM) for storing principal data, a read only memory (ROM) for storing key data, and a processing unit for writing or reading the principal data into or from the EPROM under control of the key data. The EPROM has an address converter having a volatile memory for temporarily storing the key data. External address data for wiring the principal data into the EPROM are converted to internal address data by the address converter using the key data stored in the volatile memory; the principal data stored in the EPROM are read out by converting external address data into internal address data, again using the key data stored in the volatile memory. The key data stored in the ROM are read out and applied to the volatile memory during the power turn-on of the memory system, the key data controlling the processing by the processing unit.