Synopsys Timing Constraints And Optimization User Guide 2021 -

PrimeTime is the industry standard for sign-off. The 2021 guidelines emphasize using PrimeTime (or PrimeTime SI) for final verification.

The create_clock command is the foundation of all timing constraints. It defines the clock source, period, and waveform. The period, defined with the -period option, is the length of time for one full cycle. If a clock does not have a simple 50% duty cycle, the -waveform option specifies the exact rising and falling times within the period.

Beyond setup and hold timing, the tool must honor physical design rule constraints dictated by the semiconductor foundry. These take priority over performance optimization:

Once optimization completes, you must carefully analyze the generated timing reports to identify bottlenecks. Essential Diagnostic Commands synopsys timing constraints and optimization user guide 2021

Inserting buffers to break down large capacitive loads on long nets, speeding up transitions.

: Defining arrival times at input ports relative to a clock using set_input_delay Output Delays : Specifying required times at output ports using set_output_delay Port Attributes

The quality of constraints is as important as the quality of the design itself. A final recommendation from the 2021 guide is to use constraint verification tools. The can be used to quickly check for correctness and consistency of timing constraints. Identifying issues like missing clocks, conflicting exceptions, or incomplete I/O delays early can drastically improve runtime and prevent sign-off surprises. PrimeTime is the industry standard for sign-off

Allowing multiple clock cycles for a path.

With the release of the , Synopsys has updated its definitive manual to address modern design challenges, including increasingly complex clocking schemes, advanced low-power requirements, and the nuances of next-generation geometry nodes.

Not every path in a chip needs to meet a single-cycle timing requirement. The 2021 guide highlights how to properly use exceptions to prevent the tool from "fixing" paths that aren't broken: It defines the clock source, period, and waveform

The bedrock of Synopsys timing closure is the Synopsys Design Constraints (SDC) language. Written in a Tcl-based syntax, SDC communicates your design's physical and electrical intent directly to synthesis, placement, and routing engines. The Timing Engine's Perspective

The guide introduces a "Board-Aware" constraint flow.

The guide meticulously explains the "journey" of a data signal. The process begins with a at a startpoint (like the clock pin of a register or an input port), where a clock edge pushes data onto a path. The signal then travels through a cloud of combinational logic. The journey must be completed before a capture event , where a subsequent clock edge latches the data at an endpoint (like the data pin of a register or an output port).

At the heart of the guide lies the principle of . Unlike dynamic simulation, which tests functionality using specific input vectors, STA is a much faster and more thorough method that mathematically verifies the timing performance of a design. It breaks the design into all possible timing paths, calculates the signal propagation delay along each path, and checks for violations of timing constraints.