Agere Systems Inc.

Xiaoming Yu

Miron Abramovici

Techniques for testing a sequential circuit comprising a plurality of flip-flops or other types of registers. The circuit is first configured such that substantially all feedback loops associated with the registers, other than one or more self-loops each associated with a corresponding one of the registers, are broken. Test patterns are then generated for application to the circuit. The test patterns are applied to the circuit in conjunction with partitioned clock signals each of which is associated with a corresponding level of the circuit containing at least one of the self-loops.

Sequential test pattern generation using clock-control design for testability structures

Test pattern generation is performed for a sequential circuit by first separating the circuit into overlapping pipelines by controlling corresponding clocks for one or more registers of the circuit so as to break feedback loops of the circuit, and then processing each of the pipelines separately in order to determine if particular target faults are detectable in the pipelines. Independent clocks may be provided for each of a number of registers of the circuit in order to facilitate the breaking of the feedback loops. The processing of the pipelines may include a first processing operation which detects target faults in a single time frame, and a second processing operation which detects target faults in two or more time frames. The first processing operation generates as many combinational test vectors as possible for each of the pipelines, while the second processing operation generates sequences of two or more combinational test vectors for each of the pipelines. Advantageously, the invention allows efficient combinational test pattern generation techniques to be applied to a sequential circuit.

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Champaign, IL, United States of America

Xiaoming Yu