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, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{0}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{1}$ </tex-math></inline-formula>, the logic blocks should be synchronized to the same state, and the same input sequence should be applied to them. Assuming that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{0}$ </tex-math></inline-formula> performs functional computations and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{1}$ </tex-math></inline-formula> is idle, a process described earlier synchronizes <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{1}$ </tex-math></inline-formula> to the state of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{0}$ </tex-math></inline-formula> by using a synchronization period where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{1}$ </tex-math></inline-formula> receives the input sequence of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{0}$ </tex-math></inline-formula>, and values of selected state variables are copied from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{0}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{1}$ </tex-math></inline-formula>. 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.