provides the methodology for defining timing requirements and using optimization engines to meet Performance, Power, and Area (PPA) goals Key Features and Updates (2021 Era) SDC 2.1 Support : The 2021 documentation aligns with Synopsys Design Constraints (SDC) version 2.1 , which introduced changes such as replacing the set_clock_sense command with set_sense -type clock for better clarity in constraint scripts. Fusion Technology Integration : The guide emphasizes Synopsys Fusion Technology
Timing constraints tell the synthesis and implementation tools exactly how the hardware must perform. Without accurate constraints, optimization engines may under-optimize paths (causing silicon failure) or over-optimize paths (wasting power, performance, and area). The Role of SDC
To prevent the optimization engine from over-restructuring logic that requires precise physical placement, use preservation commands.
# Disable timing analysis on a test mode signal set_false_path -from [get_ports test_mode] Use code with caution. Multicycle Paths synopsys timing constraints and optimization user guide 2021
If you are currently debugging a specific timing violation or building an SDC file, let me know:
Base clocks originate from primary input ports or internal Phase-Locked Loop (PLL) outputs.
: Incorporates technology for "low-noise" constraint verification, automatically flagging real issues (like incorrect timing exceptions) while filtering out irrelevant warnings. Automated Promotion/Demotion The Role of SDC To prevent the optimization
During pre-layout synthesis (Design Compiler), clocks are modeled as , meaning they distribute to all registers with zero delay. During post-layout implementation (IC Compiler II), after the clock tree is physically built, clocks are switched to propagated to calculate actual network delays.
addresses advanced topics that are critical for high-performance design. It explains concepts like time borrowing , where a latch can borrow time from the next clock phase to resolve a timing violation, and introduces techniques like normalized slack analysis . This metric helps identify paths that have the greatest impact on overall clock frequency, even if their absolute slack is not the worst in the design.
: Dynamically inserts clock-gating cells to save power. clocks are modeled as
Moving critical signal nets to higher, thicker metal layers that have lower resistance and capacitance. Managing Constraints During Synthesis (Design Compiler)
# Disable timing analysis between two asynchronous clock domains set_false_path -from [get_clocks clk_core] -to [get_clocks clk_audio] Use code with caution. Multi-Cycle Paths
set_output_delay specifies the time required by the external device outside the chip boundary before the next capturing clock edge.
Reorganizing logic gates to reduce the levels of logic in a critical path.