Margin (Slack)

            Input data is checked against the clock to ensure that it meets the setup and hold requirements that define the required window.

The difference between the valid and required times is called the margin. The difference between the setup time and the signals late event delay time is called the setup margin, or setup slack.

Margins may be either positive or negative. A positive margin means that the signal meets the timing requirement. A negative margin means that the signal does not meet the timing requirement. A negative margin indicates a timing violation.