Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By presence or absence pulse detection
Patent
1993-08-12
1995-06-13
Sikes, William L.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By presence or absence pulse detection
327 20, 327141, 327162, G01R 1900, H03L 700, H03K 519
Patent
active
054246610
ABSTRACT:
A sensor circuit is disclosed for use with a clock circuit providing a periodic timing signal to a clock output, wherein a timing reference for the periodic timing signal is provided by a crystal connected between a crystal input and a crystal output of the clock circuit, or alternatively provided by an external periodic logic signal coupled to the crystal input. The sensor circuit provides a sensor output in a first state, thereby indicating the presence of an external periodic logic signal timing reference, in response to at least a given number of large-signal voltage transitions on the crystal input within a certain period of time, and otherwise provides a second state on the sensor output, typically to indicate the presence of a crystal timing reference. Also disclosed is a clock circuit including a sensor circuit, and further including means for disabling a feedback resistor necessary for crystal operation when the timing reference is determined to be provided by an external periodic logic signal.
REFERENCES:
patent: 3614522 (1971-10-01), Halinski
patent: 3995272 (1976-11-01), Prill
patent: 4910703 (1990-03-01), Ikeda
patent: 5041738 (1991-08-01), Walters
patent: 5151613 (1992-09-01), Satou
Chen Hwa-Jyun
Lin San L.
Graham Andrew C.
Nguyen Tiep H.
Sikes William L.
Winbond Electronics North America Corp.
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