Hierarchical ports phase affects functional ECO quality

The backend place and route optimization process can result in hierarchical ports phase inversion moving across the boundaries between different modules. In Figure 1, you can observe that the inversion phase of port A[0] and port A[2] from Module A is shifted to Module B. While this may not pose a problem in Logic Equivalence Checking when the checking process is flattened, it can significantly impact patch size during functional ECO. Given that the most efficient and practical approach for functional ECO is module-based, it is crucial to accurately identify port phase changes in this context.

In the event that an ECO is required for port A[0] within Module A, the alterations extend to both Module A and Module B, as illustrated in Figure 2. Failure to detect the phase inversion in port A[0] having been moved to Module B can result in significant redundancy in the corrective patches for logic changes in Module B, particularly where the changes affect the fanout of port A[0]. This issue is noticeable in both functional ECO tools, GOF ECO and Conformal ECO. However, since port A[0] in Module A also needs modification, comparing the port phase between the Implementation Netlist and the Reference Netlist does not detect port A[0] phase shifting from Module A to Module B.

To resolve this problem, GOF ECO offers a solution. It accomplishes this by analyzing the Pre-layout Netlist, which is equivalent to the Implementation Netlist (Post-layout Netlist), allowing for the accurate detection of phase changes in boundary ports.

The Implementation Netlist is essentially the Pre-layout Netlist written out by the place and route tool following the backend processing. By conducting a phase comparison for port A[0] in Module A between the Implementation Netlist and the Pre-layout Netlist, any phase inversion resulting from backend tool optimizations can be readily identified. This ensures the creation of a high-quality ECO patch.

GOF platform integrates four functional components: ECO, Formal, LEC and Debug. To access detailed information about GOF, please visit the website?https://nandigits.com