Partial Scan with Pre-selected Scan Signals

A partial scan approach proposed recently selects scan signals without considering the availability of the ip-ops (FFs). Such an approach can greatly reduce the number of scan signals since maximum freedom is allowed in scan signal selection. To actually scan the selected signals, we, however, must make them FF-driving signals. In this paper, we study the problem of modifying and retiming a circuit to make a pre-selected set of scan signals FF-driving signals while preserving the set of cycles being broken. We present a new approach for solving this problem. Based on the new approach we design an efficient algorithm. Unlike a previous algorithm which inherently has no control over the area overhead incurred during the modification, our algorithm explicitly minimizes the area overhead. The algorithm has been implemented and encouraging results were obtained.