Method for incremental timing analysis

• US 6,367,056 B1
• Filed: 01/11/1999
• Issued: 04/02/2002
• Est. Priority Date: 04/23/1998
• Status: Expired due to Term

• Current Assignee: Altera Corporation (Intel Corporation)
• Original Assignee: Altera Corporation (Intel Corporation)
• Inventors: Lee, Fung Fung
• Primary Examiner(s): Smith, Matthew
• Assistant Examiner(s): Lee, Calvin
• Application Number:
  US09/228,873
• Publication Number:
  US 20020023252A1
• Time in Patent Office: 1,177 Days
• Field of Search: 716/4, 716/5, 716/6, 716/7, 716/8, 716/2, 716/18
• US Class Current: 716/113
• CPC Class Codes: G06F 30/3312 Timing analysis

Abstract

An “incremental” timing analysis or simulation uses much of the results of a previous timing simulation. The previous timing results were obtained for a previous electronic design which was slightly modified by the designer. The portion of the design affected by the modification is identified and its timing is recalculated. The timing for the remainder of the design is left as is from the previous design. The boundaries of the region affected by the design modification may be determined by various methods. If the timing analysis is performed at an early stage in the overall design process, the method chosen may be relatively simple; i.e., it need not account for load, parasitic capacitance, etc.

Claims

1. A method for performing a timing analysis on an electronic design, the method comprising:

(a) storing timing results of a first timing analysis performed on a first electronic design;

(b) modifying a portion of the first electronic design to form a second electronic design containing a modified portion and an unmodified portion;

(c) identifying an affected portion of the second electronic design where the timing results may have been locally changed as a result of the modification; and

(d) performing a second timing analysis comprising;

(i) calculating a local timing result for the affected portion of the second electronic design; and

(ii) calculating an overall timing result of the second electronic design by using the local timing result together with an unmodified timing result of the first electronic design for that portion of the first electronic design outside of the affected portion of the second electronic design.

2. The method of claim 1, wherein the first electronic design is an ASIC design.

3. The method of claim 1, wherein the first electronic design is a PLD design.

4. The method of claim 1, wherein the affected portion of the second electronic design subsumes the modified portion of the second electronic design.

5. The method of claim 1, wherein the first timing analysis is performed on a compiled PLD design.

6. The method of claim 1, wherein the first and second electronic designs on which the first and second timing analyses are performed are compiled designs.

7. The method of claim 1, wherein modifying a portion of the first electronic design involves refitting that portion of the first electronic design.

8. The method of claim 7, wherein the refitting involves repartitioning the portion of the first electronic design.

9. The EDA system of claim 8, wherein the fitter moves one or more logic cells to create the modified design.

10. The method of claim 1, wherein the modifying a portion of the first electronic design involves moving a cell in first electronic design.

11. The method of claim 10, wherein the affected portion of the second electronic design includes the fan-out from the output nodes of any cells that feed the cell that has been moved.

12. The method of claim 10, wherein the affected portion of the second electronic design includes the fan-out from the output nodes of a cell that has been moved, together with the cell that has been moved.

13. The method of claim 1, further comprising comparing the overall timing result to a timing constraint.

14. The method of claim 1, further comprising converting the timing constraint from one type to a second type.

15. The method of claim 1, wherein the overall timing results are provided in the form of Tpd.

16. A programmable logic device designed using the timing analysis of claim 1.

17. An electronic design automation system comprising:

a fitter which fits logic onto a target hardware device; and

a timing analyzer including;

(i) a delineator which identifies an affected region of a modified design where timing may have been locally changed as a result of a modification from a previous design, and

(ii) a timer which calculates the timing at nodes within the affected region.

18. The EDA system of claim 17 further comprising a database communicating with said fitter and storing design data for the modified design.

19. The EDA system of claim 18, wherein the timing analyzer obtains design data from the database, without having the design data past through the fitter.

20. The EDA system of claim 18, wherein the timing analyzer obtains the design data from the database via the fitter.

21. The EDA system of claim 18, wherein the database also stores design data associated with the previous design.

22. The EDA system of claim 17, wherein the target hardware device is a programmable logic device.

23. The EDA system of claim 17, wherein the logic fit onto the target hardware device comprises logic cells.

24. The EDA system of claim 17, wherein the fitter is provided as part of an electronic design compiler.

25. The EDA system of claim 24, wherein the compiler further includes a logic synthesizer.

26. A machine readable medium comprising instructions for performing a timing analysis on an electronic design, the instructions comprising:

(a) storing timing results of a first timing analysis performed on a first electronic design;

(b) modifying a portion of the first electronic design to form a second electronic design containing a modified portion and an unmodified portion;

(c) identifying an affected portion of the second electronic design where the timing results may have been locally changed as a result of the modification; and

(d) performing a second timing analysis comprising;

(i) calculating a local timing result for the affected portion of the second electronic design; and

(ii) calculating an overall timing result of the second electronic design by using the local timing result together with an unmodified timing result of the first electronic design for that portion of the first electronic design outside of the affected portion of the second electronic design.

27. The machine readable medium of claim 26, wherein the affected portion of the second electronic design subsumes the modified portion of the second electronic design.

28. The machine readable medium of claim 26, wherein the first timing analysis was performed on a compiled PLD design.

29. The machine readable medium of claim 26, wherein the first and second electronic designs on which the first and second timing analyses were performed are compiled designs.

30. The machine readable medium of claim 26, wherein modifying a portion of the first electronic design involves refitting that portion of the first electronic design.

31. The machine readable medium of claim 30, wherein the refitting involves repartitioning the portion of the first electronic design.

32. The machine readable medium of claim 26, wherein modifying a portion of the first electronic design involves moving a cell in first electronic design.

33. The machine readable medium of claim 32, wherein the affected portion of the second electronic design includes the fan-out from the output nodes of a cell that has been moved, together with the cell that has been moved.

34. The machine readable medium of claim 32, wherein the affected portion of the second electronic design includes the fan-out from the output nodes of any cells that feed the cell that has been moved.

35. The machine readable medium of claim 26, wherein the overall timing results are provided in the form of Tpd.

36. The machine readable medium of claim 26, wherein the instructions further specify comparing the overall timing result to a timing constraint.

37. The machine readable medium of claim 26, wherein the instructions further specify converting the timing constraint from one type to a second type.