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 1.0

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.
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

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 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		

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