What are the major files an MMMC timing run actually needs?
From PDVerse MMMC Interview Masterclass, part of the pdVerse Mentor Series
Direct answer
An MMMC timing run requires five core file types: the gate-level netlist (.v), characterized Liberty timing libraries (.lib/.db) for all PVT corners, mode-specific SDC constraint files, extracted parasitic files (SPEF) for all RC corners, and an MMMC configuration script (.tcl).
Mentor explanation
MMMC timing requires structural, physical, behavioral, and configuration inputs.
Key terms
- Gate-level netlist (.v) — structural connectivity of cells, instances, and nets.
- Liberty libraries (.lib/.db) — cell delay, transition, capacitance, and sequential timing check models per PVT point.
- SDC (.sdc) — mode-specific clocks, I/O delays, case constants, and exceptions.
- Parasitics (.spef) — per-RC-corner extracted wire resistance and capacitance.
- MMMC setup script (.tcl) — binds library sets, RC corners, delay corners, and constraint modes into active views.
Missing libraries means no delay calculation; missing SPEF causes wire delays to silently default to zero; missing MMMC scripts leaves the tool with no views to analyze.
Practical example
Directory Layout for Signoff MMMC:
project_sta/
├── netlist/design_routed.v
├── libs/
│ ├── stdcells_ssg_0.675v_125c.lib
│ └── stdcells_ffg_0.825v_m40c.lib
├── constraints/
│ ├── func_mode.sdc
│ └── scan_mode.sdc
├── parasitics/
│ ├── design_rcmax.spef
│ └── design_rcmin.spef
└── scripts/mmmc_setup.tclInterview trap
Listing only the netlist and SDC as the required files. Without characterized Liberty libraries there is no cell delay math, and without SPEF wire delay is ignored.
Key takeaways
- MMMC requires Netlist (connectivity) + Libraries (cell physics) + SDC (timing intent) + SPEF (wire parasitics) + MMMC script (binding).
- Each file type must cover the required mode and corner matrix completely.
- Missing any one file prevents the engine from generating valid signoff slack numbers.
Self-check: can you answer this aloud?
Try a 45-second answer using this structure:
- State the direct answer.
- Explain the timing or physical reason.
- Name one caveat.
- Say how you would verify it in a real flow.
MMMC Signoff Guide
Master Multi-Mode Multi-Corner Timing Signoff
Explore the full 10-chapter MMMC guide on modes, PVT corners, RC parasitics, analysis views, and correlation between implementation and signoff tools.
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