University of Wisconsin-La Crosse
To create a combinational ATPG model for an acyclic sequential circuit, all unbalanced fanouts, i.e., fanouts reconverging with different sequential depths are moved toward primary inputs using a retiming-like transformation. All flip-flops are then shorted and unbalanced primary input fanouts are split as additional primary inputs. A combinational test vector for a fault in this model is converted into a vector sequence that detects the corresponding fault in the original circuit. An analysis classifies the undetected faults in this model as either untestable or multiply-testable.