Memory system having two-level security system for enhanced prot

Details Memory system having two-level security system for enhanced prot Memory system having two-level security system for enhanced prot

1991-06-10

1994-03-08

Gossage, Glenn

Static information storage and retrieval

Magnetic bubbles

Guide structure

365195, 365201, 364DIG2, 36496576, 3649694, 395725, 380 3, G06F 1214

Patent

active

052936104

ABSTRACT:
A memory system, having security against unauthorized accessing of the contents of the memory system, comprises a first alterable memory (6), a second non-alterable memory (14, 16) and a data bus (5) for allowing external access to data stored in the memory system during a test mode of operation. The first alterable memory (6) comprises an options register (10) having a security bit (SEC) which, when programmed to an active state, prevents external access to the data stored in the first alterable memory during the test mode. The first alterable memory (6) further comprises a first data memory (8) having at least one security byte (VALSEC) which, when programmed to a predetermined state, prevents external access to the data stored in both the first alterable memory (6) and the second non-alterable memory (14, 16) during the test mode.

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patent: 5014191 (1991-05-01), Padgaonkar et al.
patent: 5175840 (1992-12-01), Sawase et al.

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