Semiconductor memory having control means for preventing unautho

Details Semiconductor memory having control means for preventing unautho Semiconductor memory having control means for preventing unautho

1990-04-24

1992-01-28

Fleming, Michael R.

Static information storage and retrieval

Read/write circuit

Erase

365195, 365228, 3642466, 36424691, 364DIG1, G06F 1200, G11C 1100

Patent

active

050848437

ABSTRACT:
A volatile storage circuit for latching data is disposed outside a non-volatile memory array. Before a bulk erase of the memory array, some of the data items contained therein are transferred to and held by the storage circuit. The data items thus saved are rewritten to the non-volatile memory array after the bulk erase, or alternatively, on the basis of control data items transferred to the storage circuit, only regions designated by these data items are subjected to the bulk erase. Thus, in case of a bulk erase of an EEPROM, some of the stored data items can be preserved, so as to prevent illicit use of and maintain the integrity of the preserved data. Also the testing time of the data rewritten to the memory array is reduced because of the elimination of the need to test the memory area containing the preserved data in that only the integrity of the memory area containing data sourced externally need be tested.

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