Static information storage and retrieval – Magnetic bubbles – Guide structure
Patent
1994-05-03
1996-03-19
An, Meng-Al
Static information storage and retrieval
Magnetic bubbles
Guide structure
395180, 365195, 380 4, 3649691, 3649692, 3649694, 364DIG2, 3642466, 3642467, 3642468, G06F 1200, G06F 1214
Patent
active
055009492
ABSTRACT:
A technique for preventing unauthorized operations in a microprocessor system provided for inhibiting access to a memory by checking specific addresses and codes, includes storing main programs and predetermined specific codes in a first memory, the execution of the specific codes by a user being prohibited; storing user programs in a second memory; respectively writing and reading the main and user programs to and from the first and second memories with a CPU; receiving address information over an address bus into a first check circuit, connected between the CPU and the first and second memories; activating a first check signal in the first check circuit to inhibit access to the first memory when an access instruction to a predetermined prohibited address is supplied by the CPU; receiving data information including instruction codes over a data bus into a second check circuit, connected between the CPU and the first and second memories; activating a second check signal in the second check circuit when instruction codes of the user program are the specific codes; receiving the first and second check signals into an inhibit circuit; and inhibiting access to the first and second memories according to the first and second check signals.
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An Meng-Al
Kabushiki Kaisha Toshiba
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