Artificially tight targets cause tool congestion, massive area inflation, and excessive power draw. report_constraint -all_violators
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Clocks are the heartbeat of any synchronous design. Accurately defining the clock network is the first and most critical step in writing an SDC file. Primary Clock Creation
Mastering Digital Design: A Comprehensive Guide to Synopsys Timing Constraints and Optimization synopsys timing constraints and optimization user guide 2021
: Defines the rise and fall edges within the period. Generated Clocks
: Selects physical cells from the target semiconductor foundry technology library ( .db ) that best satisfy the timing constraints. Essential Optimization Commands
The user guide includes a new Appendix C: "Top 20 Timing Constraint Mistakes and Fixes." SDC files use a Tcl-based syntax to describe:
The Synopsys Design Constraints (SDC) format is the industry-standard language used to communicate design intent. SDC files use a Tcl-based syntax to describe: Link environments and operating conditions Clock waveforms and characteristics Input and output delays Timing exceptions (false paths, multicycle paths) Design Environment Setup
-retime : Enables adaptive register pipelining (moving registers across combinational logic boundaries to balance slack). Structuring vs. Flattening
: Uses formal engines to ensure engineers only review legitimate timing exceptions rather than tool-generated "noise". Accessing the Guide Timing Constraints Manager | Synopsys 6. Verification with Report_timing
The create_clock command defines the period, waveform, and source of a primary clock coming into the chip from an external pin or port.
The guide also introduces versus Worst Negative Slack (WNS) . While WNS tells you the magnitude of your biggest failure, TNS gives you a bird's-eye view of the overall "health" of the design's timing. 6. Verification with Report_timing