Redundant clock system utilizing nonsynchronous oscillators
AssigneeRockwell International Corporation
InventorThomas C. McDermott, III
Life of this patent
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Abstract
A clock system is disclosed having two identical clocks not synchronized with each other. Each of the clocks includes a circuit for selecting the output of one of the clocks as the present system output. Further, each clock includes logic for detecting errors in the operation of itself, and of the other. When an error is detected in the operation of the clock selected to be the present system output, a switchover sequence control switches the output signal of the nonselected clock to become the new system output. The switchover sequence control includes a feature which ensures that the interval between pulses in the system output is greater than a predetermined period in order to minimize detrimental effects on circuitry utilizing the clock system output.
Claims18
A clock system comprising:
- first and second electronic clocks, not synchronized with each other, each including an output signal selectable as the present output of the system;
- means for selecting one of said signals;
- first means associated with said first clock for detecting errors in the operation of said first clock and of said second clock;
- second means associated with said second clock for detecting errors in the operation of said second clock and of said first clock;
- first switchover means, responsive to the detection by said first error detecting means of an error in the operation of the second clock, for switching said selecting means so that the output signal of the first clock becomes the system output, if the output signal of the second clock is said present system output;
- and
- second switchover means, responsive to the detection by said second error detecting means of an error in the operation of the first clock, for switching said selecting means so that the output signal of the second clock becomes the system output, if the output signal of the first clock is said present system output, each of said switchover means including means for switching at a time which ensures that the inverval between pulses in the system output is greater than a predetermined period.
A clock system comprised of first and second circuits capable of being separately powered and not synchronized with each other, each circuit including:
- an electronic clock;
- means for selecting the clock in one of said circuits to have a signal thereof as a present output of the system;
- means for detecting errors in the operation of the clock in the same circuit and the clock of the other circuit;
- and
- switchover means responsive to the detection by said error detecting means of an error in the operation of the clock of the other circuit, for switching so that a signal of the clock of the same circuit becomes the system output, if the clock of the other circuit was said one clock selected to be a present system output, said switchover means including means for switching at a time which ensures that the interval between pulses in the system output is greater than a predetermined period.
Dependencies are inferred from the claim text.