Reducing Test Point Area for BIST through Greater Use of Functional Flip-Flops to Drive Control Points

Recently, a new test point insertion method for pseudo-random built-in self-test (BIST) was proposed in [Yang 09] which tries to use functional flip-flops to drive control test points instead of adding extra dedicated flip-flops for driving the control points. This paper investigates methods to further reduce the area overhead by replacing dedicated flip-flops which could not be replaced in [Yang 09]. A new algorithm (alternative selection algorithm) is proposed to find candidate flip-flops out of the fan-in cone of a test point. Experimental results indicate that most of the not-replaced flip-flops in [Yang 09] can be replaced and hence even more significant area reduction can be achieved with minimizing the loss of testability.