RESTRICTED SCAN REORDERING TECHNIQUE TO ENHANCE DELAY FAULT COVERAGE

Disclosed is a method and apparatus for improved delay fault testing by optimizing the order of scan cells in a scan chain. The order of the scan cells is determined by using a cost value for an order of scan cells, the cost value being computed from costs assigned to orderings of individual pairs of scan cells. These costs can be based on the number of faults that are untestable when the pair of scan cells are placed consecutively in the scan chain. The disclosed techniques allow for enhanced delay fault coverage by rearranging scan flip-flops without increasing routing overhead.