Timothy J Short

US Patent:

56778910, Oct 14, 1997

Filed:

Nov 26, 1996

Appl. No.:

8/756565

Inventors:

Timothy A. Short - Duncanville TX
Matthew H. Childs - Arlington TX

Assignee:

National Semiconductor Corporation - Santa Clara CA

International Classification:

G11C 1300

US Classification:

36523006

Abstract:

A data security device is unitarily formed in an integrated circuit. A processor of the data security device operates in response to a clock signal provided at a clock input of the processor. Clock signal generation circuitry generates an internal clock signal. First processor-readable program code is configured to cause the processor to detect an internal, protectable, non-volatile indication of a state of the integrated circuit data security device. For example, one indication may be that non-volatile memory of the data security device has never been initialized. Another indication may be that the non-volatile memory of the data security device contains a manufacturing test pattern. Clock signal selection circuitry selectively provides a path for either the internal clock signal to be provided to the clock input of the processor or, alternatively, for an externally-provided clock signal to be provided to the clock input of the processor. Second processor-readable program code is configured to cause the processor to control the selection by the clock signal selection circuitry responsive to the state indication.

US Patent:

56047134, Feb 18, 1997

Filed:

Dec 19, 1995

Appl. No.:

8/575209

Inventors:

Timothy A. Short - Duncanville TX
Matthew H. Childs - Arlington TX

Assignee:

National Semiconductor Corporation - Santa Clara CA

International Classification:

G11C 1300

US Classification:

36523006

Abstract:

A data security device is unitarily formed in an integrated circuit. A processor of the data security device operates in response to a clock signal provided at a clock input of the processor. Clock signal generation circuitry generates an internal clock signal. First processor-readable program code is configured to cause the processor to detect an internal, protectable, non-volatile indication of a state of the integrated circuit data security device. For example, one indication may be that non-volatile memory of the data security device has never been initialized. Another indication may be that the non-volatile memory of the data security device contains a manufacturing test pattern. Clock signal selection circuitry selectively provides a path for either the internal clock signal to be provided to the clock input of the processor or, alternatively, for an externally-provided clock signal to be provided to the clock input of the processor. Second processor-readable program code is configured to cause the processor to control the selection by the clock signal selection circuitry responsive to the state indication.