How much value can testability add to a system?

Design for Testability (DFT) provides for economic benefits and reduction in costs for design, manufacturing and support of electronic systems. The amalgamation of increased benefits and net reduced costs is value enjoyed throughout the life cycle of the system. While a number of formulas have been developed over the years to justify DFT, a unifying methodology is needed that can be used to calculate the overall economic value of DFT. The methodology we use in this paper relates known input benefit and cost parameters and map their dependencies to higher level DFT benefits and costs. This method demonstrates the numerous ways DFT can improve a system´s life cycle value. It can also be used to justify the costs of DFT, such as added engineering labor, additional parts, higher cost boundary scan and built-in self test (BIST) parts. Moreover, they help convince financially focused management that DFT is a worthwhile investment even though the expenditures are in the early part of the life cycle and the return on that investment may be years later. Proponents of DFT need the methodology we present here to back up their assertions that DFT is profitable. Using dependencies lends itself to programming and calculations of DFT value can be readily performed by spreadsheet programs.