Typically a clock pin of a register or an input port.
[ RTL Code + SDC Constraints ] | v [ Translation & Elaboration ] | v [ Logic Optimization & Structuring ] <--- Cost Function Matrix | v [ Gate Mapping (Target Technology) ] | v [ Optimized Gate-Level Netlist ] The Cost Function Matrix
This guide is not static; it is the active driver of optimization. In the synthesis process (using ), the tool uses the constraints defined in the SDC file to intelligently map RTL to gates. It creates a netlist that is optimized to meet the specified clock period. synopsys timing constraints and optimization user guide 2021
| | Example SDC Command | Description | | :--- | :--- | :--- | | Basic Clock | create_clock -period 5.0 [get_ports CLK] | Creates a clock on port CLK with a period of 5.0 ns and default 50% duty cycle. | | Generated Clock | create_generated_clock -source [get_ports CLK] -divide_by 2 [get_pins U1/Q] | Creates a clock at pin U1/Q that is half the frequency of the master clock at CLK . | | Virtual Clock | create_clock -period 10.0 -name VIRT_CLK | Defines an ideal clock VIRT_CLK to be used for I/O constraints. |
Choosing appropriate logic gate structures based on path criticality. B. Post-Layout Optimization (ICC2) As of 2021, ICC2 provides advanced optimization features: Typically a clock pin of a register or an input port
The "Synopsys Timing Constraints and Optimization User Guide (2021)" is a fundamental resource for digital IC designers. It thoroughly covers the concepts, commands, and methodologies for defining timing constraints and optimizing designs with Synopsys tools. The guide remains a key reference for engineers working on high-performance digital chips.
The guide emphasizes the importance of propagating clock delays for accurate analysis. While initially clocks are ideal, after clock tree synthesis (CTS), you use the set_propagated_clock command to switch to . This results in clock delay being based on actual network parasitics and source latency, rather than a user estimate. It creates a netlist that is optimized to
The 2021 guide is built on Synopsys Design Constraints (SDC) version 2.1. While the basics remain, the guide provides critical nuance for complex SoCs.
# Create a 500 MHz clock with a 50% duty cycle on port 'clk' create_clock -name sys_clk -period 2.0 [get_ports clk] Use code with caution. Generated Clocks
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