The 2021 release did not just add new commands; it introduced a philosophical shift: . Historically, designers wrote loose constraints at the Register Transfer Level (RTL) and tightened them during physical design. The 2021 guide emphasizes signoff-quality constraints at the synthesis stage.

The user guide includes a new Appendix C: "Top 20 Timing Constraint Mistakes and Fixes."

provides a comprehensive framework for defining design intent through Synopsys Design Constraints (SDC)

: Using cross-probing between RTL, schematics, and timing reports to identify and fix bottlenecks. Managing Constraints with TCM

The Synopsys Timing Constraints and Optimization User Guide (part of the Synopsys Design Constraints or SDC standard) serves as the definitive reference for ASIC and FPGA designers using the Synopsys design flow (Design Compiler, ICC/ICC2, PrimeTime). The 2021 version reinforces the methodologies required for designing high-performance, low-power, and area-efficient integrated circuits.

Here is an example use case for timing optimization:

: Defining clocks derived from internal logic (e.g., dividers, PLLs) using create_generated_clock Clock Characteristics