Intel® Quartus® Prime Pro Edition User Guide: Scripting

ID 683432
Date 10/04/2021
Public

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Document Table of Contents

3.1.29.72. report_skew (::quartus::sta)

The following table displays information for the report_skew Tcl command:

Tcl Package and Version

Belongs to ::quartus::sta

Syntax report_skew [-h | -help] [-long_help] [-append] [-detail <summary|path_only|path_and_clock|full_path> ] [-fall_from_clock <names> ] [-fall_to_clock <names> ] [-file <name> ] [-from <names> ] [-from_clock <names> ] [-greater_than_skew <slack limit> ] [-intra_clock] [-npaths <number> ] [-panel_name <name> ] [-rise_from_clock <names> ] [-rise_to_clock <names> ] [-show_routing] [-stdout] [-through <names> ] [-to <names> ] [-to_clock <names> ]
Arguments -h | -help Short help
-long_help Long help with examples and possible return values
-append If output is sent to a file, this option appends the result to that file. Otherwise, the file will be overwritten. This option is not supported for HTML files.
-detail <summary|path_only|path_and_clock|full_path> Option to determine how much detail should be shown in the path report
-fall_from_clock <names> Valid source clocks (string patterns are matched using Tcl string matching)
-fall_to_clock <names> Valid destination clocks (string patterns are matched using Tcl string matching)
-file <name> Sends the results to an ASCII or HTML file. Depending on the extension
-from <names> Valid sources (string patterns are matched using Tcl string matching)
-from_clock <names> Valid source clocks (string patterns are matched using Tcl string matching)
-greater_than_skew <slack limit> Limit the paths reported to those with skew values greater than the specified limit.
-intra_clock Only report paths whose launch and latch clock are the same
-npaths <number> Specifies the number of paths to report for each latest and earliest arrival skew result (default=1)
-panel_name <name> Sends the results to the panel and specifies the name of the new panel
-rise_from_clock <names> Valid source clocks (string patterns are matched using Tcl string matching)
-rise_to_clock <names> Valid destination clocks (string patterns are matched using Tcl string matching)
-show_routing Option to display detailed routing in the path report
-stdout Send output to stdout, via messages. You only need to use this option if you have selected another output format, such as a file, and would also like to receive messages.
-through <names> Valid through nodes (string patterns are matched using Tcl string matching)
-to <names> Valid destinations (string patterns are matched using Tcl string matching)
-to_clock <names> Valid destination clocks (string patterns are matched using Tcl string matching)
Description

This report performs skew analysis on selected paths. As opposed to report generated by report_max_skew command, this command does not depend on the existance of set_max_skew assignments. This report computes skew with respect to the latest and the earliest arrival of each selected path. By default, "Skew for the Latest Arrival" is computed by comparing the latest arrival of each path with the earliest arrival of the path that has the smallest value for early arrival of all other paths included in the constraint. Similarly, "Skew for the Earliest Arrival" is computed by comparing the earliest arrival of each path with the latest arrival of the path that has the largest value for late arrival of all other paths included in the constraint. No path is compared with itself. Use the -stdout option to direct the report to the Tcl console (default), the -file option to write the report to a file or the -panel_name option to direct the report to the Timing Analyzer graphical user interface. You can use these options in any combination. Report skew includes data arrival times, clock arrival times, register micro parameters, clock uncertainty, on-die variation and ccpp removal. Use the -npaths option to limit the number of path result pairs reported for each set_max_skew constraint. If you do not specify this option, report_skew only reports the result pair for the single worst-case path. Use the -less_than_slack option to limit output to all paths with skew greater than the specified value, up to the number specified with -npaths. Use the -detail option to specify the desired level of report detail. "-detail path_only" (default) reports the path from the source to the destination without any detail about the clock path. Instead, the clock network delay is shown as a single number. "-detail path_and_clock" extends the arrival and required paths back to the launch and latch clocks. "-detail full_path" continues tracing back through generated clocks to the underlying base clock. The "-detail summary" option is deprecated. The -show_routing option displays detailed routing information in the path. Lines marked "IC" without the option are shown, but only as a placeholder. The routing elements for that line are broken out individually and listed before the line. The return value of this command is a two-element list. The first number is the number of paths found in the analysis. The second is the worst-case skew, in terms of the current default time unit. The "RF" column in the report output uses a two-letter symbol to indicate the rise/fall transition that occurs at that point in the path. Possible "RF" values are: Value Description ------- ------------------------------- (empty) Unknown transition R Rising output F Falling output RR Rising input, rising output RF Rising input, falling output FR Falling input, rising output FF Falling input, falling output The "Type" column in the report uses a symbol to indicate what type of delay occurs at that point in the path. Possible "Type" values are: Value Description ------- ------------------------------- CELL Cell delay COMP PLL clock network compensation delay IC Interconnect delay iExt External input delay LOOP Lumped combinational loop delay oExt External output delay RE Routing element (only for paths generated with the -show_routing option) uTco Register micro-Tco time uTsu Register micro-Tsu time uTh Register micro-Th time

Example Usage
project_open my_project
create_timing_netlist
read_sdc
update_timing_netlist

# show worst 10 paths for each earliest and latest arrival results 
report_skew -from [get_ports input[*]] -to [get_registers *] -panel_name "Report Skew" -npaths 10 -greater_than_skew 0.100 -detail full_path		

delete_timing_netlist
project_close
Return Value Code Name Code