Method and circuit for limiting access to a RAM program memory

Details Method and circuit for limiting access to a RAM program memory Method and circuit for limiting access to a RAM program memory

1989-03-17

1991-06-25

Shaw, Gareth D.

Boots, shoes, and leggings

3649692, 3649525, 3649694, G06F 1216

Patent

active

050273175

ABSTRACT:
A method and a circuit limit access to a locked portion of memory to periods when application program instructions in the locked portion of memory are being executed. An UNLOCK routine of processor instructions is executed before accessing the portion of the memory storing the application program instructions and a LOCK routine of processor instructions is executed to re-secure the memory after such access. The locking and unlocking is accomplished by addressing a comparator and transmitting data representing either a lock value or an unlock value. The comparator is connected to enable and disable decoding circuitry which in turn controls access to the locked portion of memory.

REFERENCES:
patent: 3725872 (1973-04-01), Balogh, Jr. et al.
patent: 4434464 (1984-02-01), Suzuki et al.
patent: 4439830 (1984-03-01), Chueh

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