SDF annotation provides a standardized way to back-annotate timing information into HDL simulations, enabling verification of real-world performance after synthesis and layout. The SDF 4.0 specification, defined by IEEE 1497-2001, supports both VHDL and Verilog environments and captures detailed path delays, interconnect delays, and timing checks for each design element. Simulation accuracy is enhanced by mapping the delay data directly into the simulation model using well-defined syntax and hierarchical references. This approach ensures that critical timing behaviors such as setup, hold, recovery, and removal are properly reflected in the simulation, reducing the risk of late-stage functional-timing mismatches. Understanding the internal structure of an SDF file is essential to successful annotation. The file is organized into sections that describe the delay model, hierarchical instance paths, and keyword-based timing attributes. The header includes global metadata, such as the design name, timescale, and SDF version. Timing data is defined using keywords like IOPATH, INTERCONNECT, and TIMINGCHECK, which associate specific delays with cell paths, nets, and timing conditions. Del...