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:
Apr. 17, 2001
Filed:
Jul. 14, 1998
Robert D. Patrie, Scotts Valley, CA (US);
Robert W. Wells, Cupertino, CA (US);
Steven P. Young, San Jose, CA (US);
Christopher H. Kingsley, San Jose, CA (US);
Daniel Chung, San Jose, CA (US);
Robert O. Conn, Los Gatos, CA (US);
Xilinx, Inc., San Jose, CA (US);
Abstract
A circuit measures the signal propagation delay through a selected test circuit. The test circuit is provided with an inverting feedback path so that the test circuit and feedback path together form a free-running oscillator. The oscillator then automatically provides its own test signal that includes alternating rising and falling signal transitions on the test-circuit input node. These signal transitions are counted over a predetermined time period to establish the average period of the oscillator. Finally, the average period of the oscillator is related to the average signal propagation delay through the test circuit. One embodiment of the invention includes a phase discriminator that samples the output of the oscillator and accumulates data representing the duty cycle of that signal. The duty cycle can then be combined with the average period of the test signal to determine, separately, the delays associated with falling and rising edges propagating through the test circuit.