Timing analysis method and device
A timing analysis device for preventing the amount of data and the number of analysis operations from increasing in a statistical analysis, while improving the timing convergence in a path included in a net under relatively strict timing conditions. The timing analysis device performs a static timing analysis to extract a net under relatively strict timing conditions from the analysis result and generate a timing list. The device further performs delay distribution calculation for the extracted net to analyze the delay variation in each of one or more instances included in the net. The device retrieves the timing list and sets a unique delay variation for each instance to calculate a delay distribution. The device further performs a statistical timing analysis based on the calculated delay distribution.
1 . A method for analyzing timing of a signal propagated through a path including one or more instances in a net with the use of a computer, the method comprising:
calculating a delay value for each of the instances;
performing a static timing analysis based on the delay value;
calculating a delay distribution for each of the instances based on the analysis result of the static timing analysis; and
performing a statistical timing analysis based on the analysis result and the delay distribution.
2 . The method according to claim 1 , further comprising:
extracting a net under relatively strict timing conditions based on the analysis result of the static timing analysis to generate a timing list containing information of the extracted net, wherein:
said calculating a delay distribution includes calculating a delay distribution for each of the instances in the net under the relatively strict timing conditions; and
said performing a statistical timing analysis includes performing an analysis based on the delay distribution calculated for the net under the relatively strict timing conditions and the analysis result of the static timing analysis.
3 . The method according to claim 1 , wherein said calculating a delay distribution includes calculating the delay distribution based on characteristic information indicating variation characteristics of the delay value, information indicating the calculation result of the delay value, information indicating the analysis result of the static timing analysis, and layout information of the instances.
4 . The method according to claim 1 , wherein:
said calculating a delay value for each of the instances includes defining the delay value in accordance with a delay occurrence probability value;
said calculating a delay distribution includes calculating a median value, a maximum value, and a minimum value of the delay variation distribution for each of the instances in accordance with the delay value defined for each of the instances; and
performing the statistical timing analysis includes performing the analysis by using the median value, the maximum value, and the minimum value of the delay variation distribution.
5 . The method according to claim 4 , further comprising:
calculating the delay variation distribution in accordance with a coefficient of fluctuation resulting from chip layout.
6 . The method according to claim 5 , further comprising:
correcting the delay variation distribution in accordance with a change in one or more variation conditions.
7 . The method according to claim 1 , further comprising:
extracting a first path under a relatively strict timing condition and a start point and an end point of the first path based on the analysis result of the static timing analysis; and
extracting one or more second paths excluding the first path between the start point and end point of the first path, wherein;
said calculating a delay distribution includes calculating the delay distribution related to the first path and the extracted one or more second paths; and
said performing a statistical timing analysis includes performing the statistical timing analysis related to the first path and the extracted one or more second paths.
8 . The method according to claim 7 , wherein the first path under the relatively strict timing condition is a path that includes a timing violation.
9 . The method according to claim 7 , wherein the first path under the relatively strict timing condition includes a path having a relatively low operation slack.
10 . The method according to claim 7 , wherein at least one of the one or more second paths includes a path branching from the first path.
11 . The method according to claim 7 , further comprising:
ordering the first path and the one or more second paths in an order from those of the strictest timing based on the analysis result of the static timing analysis.
12 . A device for analyzing the timing of a signal propagated through a path including one or more instances in a net, the device comprising:
a delay calculation unit for calculating a delay value for each of the instances;
a first analysis unit for performing a static timing analysis based on the delay value;
a delay distribution calculation unit for calculating a delay distribution for each of the instances based on the analysis result of the static timing analysis; and
a second analysis unit for performing a statistical timing analysis based on the analysis result and the delay distribution.
13 . The device according to claim 12 , further comprising:
a list generation unit for executing a net under relatively strict timing conditions based on the analysis result of the static timing analysis to generate a timing list containing information of the extracted net, wherein:
the delay distribution calculation unit calculates the delay distribution for each of the instances in the net under the relatively strict timing conditions; and
the second analysis unit performs the statistical timing analysis based on the delay distribution calculated for the net under the relatively strict timing conditions and the analysis result of the static timing analysis.
14 . The device according to claim 13 , wherein the delay distribution calculation unit calculates the delay distribution based on characteristic information indicating variation characteristics of the delay value, information indicating the calculation result of the delay value, information indicating the analysis result of the static timing analysis, and layout information of the instances.
15 . The device according to claim 14 , wherein:
the delay calculation unit defines a delay value for each of the instances in accordance with a delay occurrence probability value;
the delay distribution calculation unit calculates a median value, a maximum value, and a minimum value of the delay variation distribution for each of the instances in accordance with the delay value defined for each of the instances; and
the second analysis unit performs the statistical timing analysis by using the median value, the maximum value, and the minimum value of the delay variation distribution.
16 . The device according to claim 12 , further comprising:
a first extraction unit for extracting a first path under a relatively strict timing condition and a start point and an end point of the first path based on the analysis result of the static timing analysis; and
a second extraction unit for extracting one or more second paths excluding the first path between the start point and end point of the first path, wherein;
the delay distribution calculation unit calculates the delay distribution related to the first path and the extracted one or more second paths; and
the second analysis unit performs the statistical timing analysis related to the first path and the extracted one or more second paths.
17 . The device according to claim 16 , wherein the first path under the relatively strict timing condition is a path that includes a timing violation.
18 . The device according to claim 16 , wherein the first path under the relatively strict timing condition includes a path having a relatively low operation slack.
19 . The device according to claim 16 , wherein at least one of the one or more second paths includes a path branching from the first path.
20 . The device according to claim 16 , wherein the second analysis unit orders the first path and the one or more second paths in an order from those of the strictest timing based on the analysis result of the static timing analysis.