Bruce A Rudolph, 75Montrose, PA

6182237, Jan 30, 2001

Aug 31, 1998

9/144758

Timothy C. Bronson - Vestal NY
Bruce G. Rudolph - Rochester MN

International Business Machines Corporation - Armonk NY

G06F 112

713503

A phase error detection circuit apparatus and method for detecting phase misalignment between first clock signals operating in a slow time domain and second clock signals operating in a fast time domain. A frequency divider and shift register are clocked in the slow time domain to sequentially sample all possible alignments of the first clock signals. A second shift register is clocked in the fast time domain and operates responsive to the output of the frequency divider and shift register to generate a phase alignment error signal when the phase alignment is incorrect or the frequency divider is not switching in a correct cycle. Error detection logic clocked in the slow time domain samples and optionally masks the phase error signal. State machine logic may be provided to generate an output error signal when each possible phase alignment results in a phase alignment error signal.