Intel® Quartus® Prime Pro Edition User Guide: Scripting

ID 683432
Date 10/04/2021
Public

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3.1.29.57. report_max_skew (::quartus::sta)

The following table displays information for the report_max_skew Tcl command:

Tcl Package and Version

Belongs to ::quartus::sta

Syntax report_max_skew [-h | -help] [-long_help] [-append] [-detail <summary|path_only|path_and_clock|full_path> ] [-file <name> ] [-less_than_slack <slack limit> ] [-npaths <number> ] [-panel_name <name> ] [-show_routing] [-stdout]
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
-file <name> Sends the results to an ASCII or HTML file. Depending on the extension
-less_than_slack <slack limit> Limit the paths reported to those with slack values less than the specified limit.
-npaths <number> Specifies the number of paths to report for each latest and earliest arrival skew result per set_max_skew assignment (default=1)
-panel_name <name> Sends the results to the panel and specifies the name of the new panel
-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.
Description

Reports max skew analysis results for all set_max_skew commands in a single report. For each valid set_max_skew constraint, this command computes skew with respect to the latest and the earliest arrival of each 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. 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_max_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 slack less than the specified value, up to the number specified with -npaths. Use the -detail option to specify the desired level of report detail. The -detail summary option generates a single table listing only the highlights of each path (and is the same as -summary option, which this replaces. "-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 -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 slack, 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

# create max skew constraints
set_max_skew -from [get_ports data_ports[*]] -to [get_keepers *] 0.200
set_max_skew -from [get_keepers *] -to [get_ports output_ports[*]] 0.100

# show worst 10 paths for each earliest and latest arrival results 
# per max_skew assignment assuming that their slack is less than 0.100
report_max_skew -panel_name "Report Max Skew" -npaths 10 -less_than_slack 0.100 -detail full_path		

delete_timing_netlist
project_close
Return Value Code Name Code String Return
TCL_OK 0 INFO: Operation successful
TCL_ERROR 1 ERROR: Timing netlist does not exist. Use create_timing_netlist to create a timing netlist.
TCL_ERROR 1 ERROR: Report database is not open

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