Timing Constraints (SDC)

VLSI Concept · Synthesis

Tell the tool what 'fast enough' means, in writing.

Before synthesis can optimize anything, it needs a contract: what's the clock frequency, which paths are exempt, how much delay is allowed on inputs/outputs. This is written as SDC (Synopsys Design Constraints) — without accurate constraints, a synthesis tool has no idea what "correct timing" even means for your design.

Examplecreate_clock -period 2.0 [get_ports clk]

Why it mattersAn under-constrained design will synthesize "successfully" and still fail in silicon because nobody told the tool the real target.

Common mistakeMissing constraints on asynchronous or generated clocks, leading tools to silently ignore real timing paths.

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