IR flow based on vector or vectorless? Is toggle rate given? twf fiile, what's its contents?

o   Vector-based Analysis: Used VCD (Value Change Dump) or FSDB files generated from gate-level simulations of specific, high-activity scenarios (e.g., boot-up sequence, high-performance benchmark execution, specific test modes). These vectors provide accurate, cycle-by-cycle switching activity for those specific scenarios, allowing us to identify peak IR drop and EM stress under known critical operating conditions

o   Vectorless Analysis: To ensure broader coverage and identify potential worst-case scenarios not easily captured by specific VCDs, used vectorless dynamic analysis.

o   Usually Vectorless is often used earlier in the flow for faster feedback, while vector-based analysis with critical scenarios mandatory for final signoff

o   Given Toggle Rate? à Yes, toggle rates were used, primarily for:

o   Static IR Drop/Power Analysis: Average toggle rates (often derived from synthesis estimates, statistical propagation, or averaged from simulations) used along with leakage data to calculate the average current for static analysis.

o   Vectorless Dynamic Analysis (Seeding): Some vectorless techniques might use initial toggle rate information as a starting point for activity propagation or statistical analysis.

o   Given TWF file? Yes, TWF (Timing Window File) files were used as input for dynamic analysis, especially for vectorless methods

o   A TWF file contains information about the possible switching time windows for signals in the design.

o   For each net or pin, it specifies the earliest and latest possible time (relative to the clock edge) that a signal transition (rise or fall) can occur