International Business Machines Corporation

William C Laviola

Daniel Francis Casper

Frank David Ferraiolo

Robert S Capowski

Richard C Jordan

Peter R Tomaszewski

A self-timed interface (STI) in which a clock signal clocks bit serial data onto a parallel, electrically conductive bus and the clock signal is transmitted on a separate line of the bus. The received data on each line of the bus is individually phase aligned with the clock signal. The received clock signal is used to define boundary edges of a data bit cell individually for each line and the data on each line of the bus is individually phase adjusted so that, for example, a data transition position is in the center of the cell.

Self timed interface

An edge detector has a digital phase locking loop in which one of the signals (e.g., the data signal) is coupled to a delay chain that develops a series of incrementally phase delayed versions of the input. Adjacent phase delayed pairs are selected, one pair at a time, and are compared to the other signal (e.g., the clock signal) to determine if an edge of the clock falls between the edges of the data signal in the selected phase pair, or falls outside the edges of the selected phase pair, on one side or the other thereof. If the clock edge falls outside the selected pair, a control signal selects another pair for comparison and the process is repeated until, for example, the data edges are aligned with the positive going edge of the clock. With a clock frequency equal to twice data frequency, the data can then be sampled on the falling edge of the clock.

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Round Rock, TX, United States of America

William C Laviola