Quo Vadis Signal? Automated Directionality Extraction for Post-Programming Verification of a Transistor-Level Programmable Fabric

We discuss the challenges related with developing a post-programming verification solution for a TRAnsistor-level Programmable fabric (TRAP). Toward achieving high density, the TRAP architecture employs bidirectionally-operated pass transis-tors in the implementation of its logic and interconnect network. While it is possible to model such transistors through appropriate primitives of hardware description languages (HDL) to enable simulation-based validation, Logic Equivalence Checking (LEC) methods and tools do not support such primitives. As a result, formally verifying the functionality programmed by a given bit-stream on TRAP is not innately possible. To address this limitation, we introduce a method for automatically determining the signal flow direction through bidirectional pass transistors for a given bit-stream and subsequently converting the HDL describing the programmed fabric to consist only of unidirectional transistors. Thereby, commercial EDA tools can be used to check logic equivalence between the transistor-level HDL describing the programmed fabric and the post-synthesis gate-level netlist.