Patent ID: 7373538

Claim:
A method for determining incremental differences in propagation delay comprising: determining a first propagation delay by: programmably coupling a first plurality of interconnect lines in series to provide a first signal path; programmably coupling a first end of the first signal path to a first sequential circuit and a second end of the first signal path to a second sequential circuit; receiving a first input to an input port of the first sequential circuit; clocking out the first input from a first output port of the first sequential circuit to the first signal path responsive to a clock signal; receiving the first input from the first signal path to a clock port of the second sequential circuit, the first input being delayed by the first signal path; clocking out a second input received to an input port of the second sequential circuit responsive to the first input as delayed by the first signal path; and determining the first propagation delay of the first input associated with traversing the first signal path; determining a second propagation delay by: programmably coupling a second plurality of interconnect lines in series to provide a second signal path, the second plurality of interconnect lines being the first plurality of interconnect lines except for at least a first interconnect line in the first plurality of interconnect lines being swapped for a second interconnect line not in the first plurality of interconnect lines; programmably coupling a first end of the second signal path to the first sequential circuit and a second end of the second signal path to the second sequential circuit; receiving a third input to the input port of the first sequential circuit; clocking out the third input from the first output port of the first sequential circuit to the second signal path responsive to the clock signal; receiving the third input from the second signal path to the clock port of the second sequential circuit, the third input being delayed by the second signal path; clocking out a fourth input responsive to the third input as delayed by the second signal path; and determining the second propagation delay of the third input associated with traversing the second signal path; and comparing the first propagation delay to the second propagation delay to determine a propagation delay difference associated with the first and second signal paths.