A protocol extraction strategy for control point insertion in design for test of transition signaling circuits

Control/observation points have been used to detect undetectable faults in delay-insensitive/speed-independent circuits but no techniques exist so far for its use in reducing the test length. The major difficulty is in deriving a safe hazard-free test. A theory for control point insertion is presented for the purpose of test length reduction of transition signaling circuits. It is based on extraction of safe behaviors from the original usage protocol via gap detection (identification of unnecessary behavior) and gap matching (jumping from one partial state to another). The area overhead is low, requires only a single input pad, and can give significant reductions in test length.