What is clock skew in VLSI?

What is clock skew?

In a synchronous circuit clock skew is the difference in the arrival time between two sequentially-adjacent registers.

How is clock skew calculated?

Clock Skew is the delay difference between the source (SRC) clock path and the destination (DST) clock path. The rough calculation is Clock Skew = DST clock delay – SRC clock delay.

What is meant by clock uncertainty?

Clock uncertainty is the time difference between the arrivals of clock signals at registers in one clock domain or between domains. Pre-layout and Post-layout Uncertainty. Pre CTS uncertainty is clock skew, clock Jitter and margin. After CTS skew is calculated from the actual propagated value of the clock.

What is maximum clock skew?

Clock skew is the maximum time difference between the active clock edges for any two clocked elements. Clock skew is viewed as an uncertainty on the position of the active clock edge, and as the skew increases larger margins must be allocated for the setup and hold times of the clocked registers.

How do you handle a clock skew?

Reducing the Clock skew to the minimum is the best approach to reduce the risk of short-path problems. Maintaining the clock skew at a value less than the smallest Flop-to-Flop delay in the design will improve the robustness of the design against any short-path problems.

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How do you stop a clock skew?

The simplest method to help prevent the short data path problem is to minimize the clock skew by using the low-skew global routing resources for clock signals. Microsemi devices provide various types of global routing resources that significantly reduce skew.

How do I reduce jitter time?

Decreasing the jitter of the system clock circuit can be achieved in many ways, including improving the clock source, as discussed, as well as filtering, frequency division, and proper choice of clock circuit hardware.

What is skew balancing?

However, not all clock end points need to be balanced with each other; these different groups have different clock end points, better known as ‘skew groups. ‘ Balancing them separately from each other traditionally means writing multiple CTS specs by hand and performing multiple CTS runs.

What is clock margin?

Timing margin is an electronics term that defines the difference between the actual change in a signal and the latest time at which the signal can change in order for an electronic circuit to function correctly.

Why setup uncertainty is more than hold uncertainty?

hold time always less than setup time

at synthesis stage, more concern on reduce path timing, so setup uncertainty is more important to add margin to design. hold is easy fix, so less important, when do timing check, you should set a more consertive hold uncertainty .