Meaning
Timing analysis methodologies that evaluate the propagation delay of all digital signals across a design without simulating the functional logic patterns verify the timing margins. Running static timing analysis ensures that every path in the circuit meets the setup and hold requirements under all operating corners. This check is performed during the physical implementation flow of integrated circuits and field-programmable gate arrays.
Delay Calculation
Cell delays are calculated using library data that characterizes each gate for various input transition speeds and output load capacitances. The tool also extracts the metal trace parasitics from the physical layout to determine the wire delays. These values are combined to compute the arrival times of all signals at the register inputs.
This calculation is performed for both fast and slow process conditions.
Critical Path
Analysis runs identify the paths with the least timing margin, known as the worst-case paths. Designers focus on these paths to optimize the layout or adjust the logic to achieve the desired clock frequency. If the margin is negative, the design cannot run reliably at the target speed.
Automation tools can automatically restructure the logic to fix these worst-case paths.
Timing Coverage
Exhaustive evaluation of all paths ensures that no hidden timing hazards remain in the design. This complete coverage represents a massive advantage over functional simulation runs, which can easily miss timing violations on unused paths. Dynamic simulation of these paths would require an impossible number of test patterns.
Using this exhaustive approach provides a complete verification of the circuit’s temporal performance.
