Synopsys Timing Constraints And Optimization User Guide 2021 |top| -

The 2021 guide focuses on Synopsys Design Constraints (SDC). This is the language used to write the rules. Here are the main topics the guide covers. 1. Setting Up Clocks

Use formal techniques to validate that SDC constraints match the functional intent, eliminating silicon failure risks caused by incorrect exceptions. 3. Optimization Techniques in Design Compiler (2021)

A false path is a path that exists topologically in the netlist but cannot execute logically, or a path that does not need to be timed (e.g., static configuration registers). synopsys timing constraints and optimization user guide 2021

Used for asynchronous resets or synchronizer chains where timing analysis is irrelevant.

In certain architectures—such as multi-stage hardware multipliers or data buses throttled by an enable signal—the data is intentionally designed to take multiple clock cycles to stabilize before being captured. The 2021 guide focuses on Synopsys Design Constraints (SDC)

The underlying principle is simple but critical: timing constraints define the performance targets that synthesis and physical design tools must meet. Errors in constraint specification, such as a misapplied false path or incorrect case analysis constant, can lead to the chip failing to function (i.e., "turning the chip into a brick"). This makes the guidance in the user guide essential for ensuring design success.

# Prioritize timing over area considerations during compile set_max_area 0 # Fix hold time violations automatically during synthesis (compile_ultra) set_fix_hold [all_clocks] # Enable high-effort optimization for aggressive timing closure compile_ultra -retime -gate_clock Use code with caution. Optimization Techniques in Design Compiler (2021) A false

The guide concludes with a "Best Practices" section, highlighting common errors:

, which enables a unified timing analysis engine across synthesis, placement, and routing to ensure timing signoff correlation and reduce iterations. Advanced Timing Analysis All-Aware Analysis

Not all paths should be constrained by a single clock period. The user guide explains how to use to override default single-cycle timing checks. The primary commands for this are:

Use set_max_fanout constraints or manually insert buffers to distribute the load.