Methods for identifying failing timing requirements in a digital design

• US 7,886,246 B2
• Filed: 04/16/2008
• Issued: 02/08/2011
• Est. Priority Date: 04/16/2008
• Status: Active Grant

• Current Assignee: Siemens Industry Software Inc. (Siemens AG)
• Original Assignee: International Business Machines Corporation
• Inventors: Dubuque, John P., Buck, Nathan C., Foreman, Eric A., Habitz, Peter A., Visweswariah, Chandramouli
• Primary Examiner(s): Doan; Nghia M
• Application Number:
  US12/103,845
• Publication Number:
  US 20090265674A1
• Time in Patent Office: 1,028 Days
• Field of Search: 716 4- 6, 716/18, 703 13- 14
• US Class Current: 716/108
• CPC Class Codes: G06F 30/3312 Timing analysis

Abstract

Methods for identifying failing timing requirements in a digital design. The method includes identifying at least one timing test in the digital design that has a passing slack in a base process corner and a failing slack in a different process corner. The method further includes computing a sensitivity of the failing slack to each of a plurality of variables and comparing each sensitivity to a respective sensitivity threshold. If the sensitivity of at least one of the variables is greater than the respective sensitivity threshold, then the at least one timing test is considered to fail.

Claims

1. A method of identifying failing timing requirements in a digital design, the method comprising:

identifying, with a computer, at least one timing test in the digital design that has a passing slack in a base process corner and a failing slack in a different process corner, wherein the failing slack is computed via slack extrapolation by subtracting a multiple of the standard deviation of the sensitivity of the extrapolated failing slack to a first group of the variables from a mean slack and subtracting a multiple of the sensitivity of the extrapolated failing slack to a second group of the variables from the mean slack;

computing a sensitivity of the failing slack to each of a plurality of variables of the at least one timing test;

comparing each sensitivity to a respective sensitivity threshold; and

if the sensitivity of at least one of the variables is greater than the respective sensitivity threshold and the projected failing slack is reduced due to the at least one of the variables moving to the opposite corner, determining with the computer that the at least one timing test fails if the at least one of the variables is not part of a variable group.

2. The method of claim 1 further comprising:

using the at least one timing test for timing closure during timing optimization.

3. The method of claim 1 further comprising:

computing the failing slack via multi-corner timing analysis.

4. The method of claim 1 further comprising:

computing the failing slack via statistical static timing analysis.

5. The method of claim 1 further comprising:

if the at least one sensitivity of the failing slack is greater than the respective sensitivity threshold, fixing the failing slack or the at least one sensitivity in advance of a subsequent timing run.

6. A method of identifying failing timing requirements in a digital design, the method comprising:

identifying, with a computer, at least one timing test in the digital design that has a passing slack in a base process corner and a failing slack in a different process corner, wherein the failing slack is computed via slack extrapolation by subtracting a multiple of the standard deviation of the sensitivity of the extrapolated failing slack to a first group of the variables from a mean slack and subtracting a multiple of the sensitivity of the extrapolated failing slack to a second group of the variables from the mean slack;

computing a sensitivity of the failing slack to each of a plurality of variables of the at least one timing test;

comparing each sensitivity to a respective sensitivity threshold;

if at least one sensitivity of the projected failing slack is greater than the respective sensitivity threshold, determining with the computer that the at least one timing test fails unless at least one of the variables is not flipped and the at least one of the variables is not part of a variable group.

7. The method of claim 6 further comprising:

using the at least one timing test for timing closure during timing optimization.

8. The method of claim 6 further comprising:

computing the failing slack via multi-corner timing analysis.

9. The method of claim 6 further comprising:

computing the failing slack via statistical static timing analysis.

10. The method of claim 6 further comprising:

if the at least one sensitivity of the failing slack is greater than the respective sensitivity threshold, fixing the failing slack or the at least one sensitivity in advance of a subsequent timing run.