Partial scan design based on circuit state information

State information of a sequential circuit can be used to evaluate the complexity of test generation. The ratio of valid states to all the states of the circuit is an important indicator of test generation complexity. Using valid states obtained via logic simulation, a testability measure based on the density of encoding is proposed for scan flip flop selection. A second testability measure based on the test generation state information is also presented and used to select scan flip flops. Cycles are broken selectively on the basis of the circuit state information. Good fault coverage and test efficiency are obtained when fewer scan flip flops than the minimum cut set are selected. Experimental results are presented to demonstrate the effectiveness of the method.