Retry-Based Synchronization for Online Testing of Identical Logic Blocks

State-of-the-art designs include identical instances of logic blocks to support parallel computations. Identical logic blocks at close physical proximity can be tested online by comparing their output sequences. This removes the need for known input and output sequences. To use output comparison for two logic blocks, $B_{0}$ and $B_{1}$ , the logic blocks should be synchronized to the same state, and the same input sequence should be applied to them. Assuming that $B_{0}$ performs functional computations and $B_{1}$ is idle, a process described earlier synchronizes $B_{1}$ to the state of $B_{0}$ by using a synchronization period where $B_{1}$ receives the input sequence of $B_{0}$ , and values of selected state variables are copied from $B_{0}$ to $B_{1}$ . A single synchronization period was used earlier. The first key contribution of this article is to introduce a retry-based synchronization process with multiple synchronization periods to avoid flagging synchronization failures as faults. The second contribution of this article is to develop the synchronization process in a simulation environment that considers functional operation conditions. Experimental results for benchmark circuits demonstrate the effectiveness of the retry-based process and the importance of the functional simulation environment.