Broadside and Functional Broadside Tests for Partial-Scan Circuits

Functional broadside tests were defined to address overtesting that may occur due to the detection of delay faults under nonfunctional operation conditions. Such conditions are made possible by scanning in unreachable states. Functional broadside tests were defined and studied in the context of full-scan circuits. In this work, we study the definition of broadside and functional broadside tests in partial-scan circuits. A unique property we show is that if the unscanned state variables are observable (through the application of input sequences or through observation points), the fault coverage achievable with functional broadside tests is independent of the level of scan and the subset of scanned state variables. This implies that when functional broadside tests are used to avoid overtesting, using lower percentages of scanned state variables may be possible without reducing the fault coverage significantly. Experimental results support this point.