Functional Broadside Tests Under an Expanded Definition of Functional Operation Conditions

The functional operation of a synchronous sequential circuit is defined to start after the circuit is initialized to a known state, typically by a synchronizing sequence. The states that the circuit can visit after it is synchronized are called reachable states, and functional operation consists of state transitions between reachable states. We expand the definition of functional operation to include all the state transitions that may be traversed during the application of the synchronizing sequence. This adds certain state transitions that involve unreachable states to the definition of functional operation. Expanding the definition of functional operation is justified by the fact that the circuit needs to be designed for correct operation during the synchronization process. It is advantageous when functional broadside tests are used to avoid overtesting. We study the effect of the expanded definition on the coverage of transition faults.