Sage-Tips

What is static timing analysis?

A setup constraint specifies how much time is necessary for data to be available at the input of a sequential device before the clock edge that captures the data in the device. This constraint enforces a maximum delay on the data path relative to the clock edge.

How do you perform a static timing analysis?

To check a design for violations or say to perform STA there are 3 main steps:

1. Design is broken down into sets of timing paths,
2. Calculates the signal propagation delay along each path.
3. And checks for violations of timing constraints inside the design and at the input/output interface.

What is static and dynamic timing analysis?

Dynamic timing analysis verifies functionality of the design by applying input vectors and checking for correct output vectors whereas Static Timing Analysis checks static delay requirements of the circuit without any input or output vectors.

Why do we need static timing analysis?

The main goal of static timing analysis is to verify that despite these possible variations, all signals will arrive neither too early nor too late, and hence proper circuit operation can be assured. Since STA is capable of verifying every path, it can detect other problems like glitches, slow paths and clock skew.

What is the main objective of timing closure?

The term is also used for the goal that is achieved, when such a design has reached the end of the flow and its timing requirements are satisfied. The main steps of the design flow, which may be involved in this process, are logic synthesis, placement, clock-tree synthesis and routing.

What is setup time and hold time?

Setup time is the amount of time required for the input to a Flip-Flop to be stable before a clock edge. Hold time is similar to setup time, but it deals with events after a clock edge occurs. Hold time is the minimum amount of time required for the input to a Flip-Flop to be stable after a clock edge.

What is WNS and TNS in VLSI?

WNS = Worst Negative Slack. TNS = Total Negative Slack = sum of the negative slack paths.

What is meant by timing closure?

Timing closure is the process by which a logic design consisting of primitive elements such as combinatorial logic gates ( and , or , not , nand , nor , etc.) and sequential logic gates (flip flops, latches, memories) is modified to meet its timing requirements.

What is Static Static timing analysis?

Static timing analysis (STA) is a simulation method of computing the expected timing of a digital circuit without requiring a simulation of the full circuit. High-performance integrated circuits have traditionally been characterized by the clock frequency at which they operate.

What types of paths does Sta consider for timing analysis?

STA also considers the following types of paths for timing analysis: Clock path. A path from a clock input port or cell pin, through one or more buffers or inverters, to the clock pin of a sequential element; for data setup and hold checks. Clock-gating path.

What is the best way to perform timing analysis?

Another way to perform timing analysis is to use dynamic simulation, which determines the full behavior of the circuit for a given set of input stimulus vectors. Compared to dynamic simulation, static timing analysis is much faster because it is not necessary to simulate the logical operation of the circuit.

What are the timing paths in a logic cloud?

The following figure shows the timing paths in a simple design example: A combinational logic cloud might contain multiple paths, as shown in the following figure. STA uses the longest path to calculate a maximum delay and the shortest path to calculate a minimum delay. STA also considers the following types of paths for timing analysis: