The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 17, 1997
Filed:
Aug. 24, 1995
Timothy Don Davis, Arlington, TX (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A secure time keeping peripheral device is for synchronizing a time reference clock signal to a system clock signal and is especially suited for use in low-power processor applications. Time reference circuitry adjusts a time reference counter held therein responsive to transitions of the time reference clock signal. At least one system time register is connected to the time reference circuitry to receive the time reference counter responsive to transitions of a synchronizing signal. Synchronizing signal generating circuitry is connected to receive the system clock signal and to provide the synchronizing signal, synchronous to the system clock signal, when an externally provided enable signal is asserted to the synchronizing signal generating circuitry. Since the system time register circuitry is only sampled when the externally provided enable signal is asserted (e.g., when the processor needs to determine the value of the 'real time clock'), power consumption by the secure time keeping device is greatly reduced relative to power consumption of conventional secure time keeping devices.