What are TLUPlus and RC technology files, and why is a layer map needed?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
RC technology models translate interconnect geometry into resistance and capacitance. TLUPlus is a layer-specific parasitic model used by ICC2 native extraction; layer mapping aligns the extraction model's layer names with the implementation technology.
Technical Explanation
Cell timing models describe cell behavior, but wires add delay and load too. Their electrical behavior depends on geometry and the process stack. A long, thin wire behaves differently from a short, wide one, and nearby conductors affect capacitance. Before routing, tools estimate interconnect; after routing, more detailed geometry is available for extraction. The supplied Timing Analysis guide describes reading TLUPlus models with read_parasitic_tech and associating them with corners using set_parasitic_parameters. Reading a model and selecting it for a corner are separate actions. The guide also describes more advanced extraction paths, so TLUPlus should not be presented as the only possible extraction technology in every flow. If the technology calls a layer M1 while the extraction model calls it METAL1, a validated layer map establishes the correspondence. A map is not permission to combine different process stacks: the underlying physical meanings must match. Check conducting layers, vias, units, the model's intended corner, and the early/late assignments. Use the methodology's qualified files rather than constructing mappings from similar-looking names alone.
Common Mistake
Loading two files and assuming ICC2 has automatically assigned them to all intended timing corners.
Follow-up Question & Model Response
How do you separate a layer-map issue from a bad timing constraint? Check extraction/model diagnostics and actual RC assignments before changing the SDC.
Practical Example
A setup corner might select an approved late RC model while a hold calculation uses an approved early model. The correct combinations come from the signoff matrix; RCmax is not a universal synonym for the worst case of every path.
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