report_clock_uncertainity - 2025.2 English - UG835

Vivado Design Suite Tcl Command Reference Guide (UG835)
Document ID
UG835
Release Date
2025-11-20
Version
2025.2 English

Description

This command reports the components of the total clock uncertainty. It applies to the specific timing paths or between clock pairs and requires an open synthesized or implemented design. The command is applicable only on Versal devices.

The Period, Transfer, and System Jitter columns report the key values for the clock pair. For the details on each clock, refer to the detailed report.

Note: By default, the report is available in the Tcl console or STD output. You can also write results to a file or return them as a string.

Arguments

-of_objects <args> - (Optional) Reports the clock uncertainty on the specified timing path objects. It is used with the get_timing_paths command.

Tip: Do not use -of_objects for the following:
  • with -from or -to options which identifies clock pairs
  • with -setup or -hold

-from <args> - (Optional) Specifies the source clocks of the clock pairs relationship which analyzes the clock uncertainty. You can specify clock names or clock objects.

-rise_from <args> - (Optional) Similar to the -from option, but considers only the rising edge of the source clocks for the clock uncertainty report.

-fall_from <args> - (Optional) Similar to the -from option, but considers only the falling edge of the source clocks for the clock uncertainty report.

-to <args> - (Optional) Specifies the destination clocks of the clock pairs relationship which analyzes the clock uncertainty. You can specify clock names or clock objects.

-rise_to <args> - (Optional) Similar to the -to option, but considers only the rising edge of the destination clocks for the clock uncertainty report.

-fall_to <args> - (Optional) Similar to the -to option, but considers only the falling edge of the destination clocks for the clock uncertainty report.

-setup - (Optional) Report the clock uncertainty for setup analysis.

-hold - (Optional) Report the clock uncertainty for hold analysis.
Note: You can specify -setup and -hold together.
-details - (Optional) Provide a detailed breakdown report on the timing paths or clock pairs.
Note: By default, it only report a summary table.

-significant_digits <arg> - (Optional) Specifies the number of significant digits in the output results. The valid range is from 0 to 3. The default setting is 3 significant digits.

-no_header - (Optional) Do not write a header to the report.

-file <arg> - (Optional) Writes the report into a specified file. If -append option is not specified, it overwrites the existing file.

Note: If the path is not specified, the file is saved either into current working directory or launch directory.

-append - (Optional) Append the output of the command to the specified file rather than overwriting it.

Note: The -append option can only be used with the -file option.

-return_string - (Optional) Directs the output to a Tcl string rather than to the standard output. A variable definition captures the Tcl string, parses, or processes as required.

Note: This argument cannot be used with the -file option.

Examples

The following example reports the clock uncertainty on the worst setup path: 
report_clock_uncertainty -of_objects [get_timing_paths]

The following example reports the clock uncertainty for clock domain crossings either from a clock specified by name or to another specified as a clock object: 

report_clock_uncertainty -from clk_pin_p -to [get_clocks clk_rx_clk_core]

The following example reports the clock uncertainty for the rising clock edge of clk_out0_1 to any other clock:

report_clock_uncertainty -rise_from clk_out0_1 -to [get_clocks]

See Also