set_clock_uncertainty (::quartus::sdc)

The following table displays information for the set_clock_uncertainty Tcl command:

Tcl Package and Version

Belongs to ::quartus::sdc 1.5

Syntax set_clock_uncertainty [-h | -help] [-long_help] [-add] [-enable_same_physical_edge] [-fall_from <fall_from_clock> ] [-fall_to <fall_to_clock> ] [-from <from_clock> ] [-hold] [-rise_from <rise_from_clock> ] [-rise_to <rise_to_clock> ] [-setup] [-to <to_clock> ]
<uncertainty>
Arguments -h | -help Short help
-long_help Long help with examples and possible return values
-add Specifies that this assignment is an addition to the clock uncertainty derived by derive_clock_uncertainty call
-enable_same_physical_edge Enable setting uncertainty value for same physical clock edge
-fall_from <fall_from_clock> Valid destinations (string patterns are matched using Tcl string matching)
-fall_to <fall_to_clock> Valid destinations (string patterns are matched using Tcl string matching)
-from <from_clock> Valid destinations (string patterns are matched using Tcl string matching)
-hold Only apply the uncertainty value to hold and removal checks
-rise_from <rise_from_clock> Valid destinations (string patterns are matched using Tcl string matching)
-rise_to <rise_to_clock> Valid destinations (string patterns are matched using Tcl string matching)
-setup Only apply the uncertainty value to setup and recovery checks
-to <to_clock> Valid destinations (string patterns are matched using Tcl string matching)
<uncertainty> Uncertainty
Description 
Specifies clock uncertainty or skew for clocks or
clock-to-clock transfers. You can specify uncertainty
separately for setup and hold, and you can specify
separate rising and falling clock transitions. If you omit 
specifying -setup or -hold the uncertainty value will be
applied to both analysis types.  Similarly, if you omit
specifying rising or falling clock transitions the uncertainty
value will be applied to both transitions.
The	setup uncertainty is subtracted from the data required
time for each applicable path, and the hold
uncertainty is added to the data required time for
each applicable path.

When you use the -add option, the clock uncertainty
assignment is treated as an addition to the value
calculted by the derive_clock_uncertainty command for
a particular clock transfer, overriding previous
uncertainty assigments made with or without the -add
option. Note that when you do not use the -add option
but still call derive_clock_uncertainty, clock
uncertainty assignments you create take priority. When
you do not use the derive_clock_uncertainty command,
using the set_clock_uncertainty command with -add
option has the same effect as without the -add option.

Note: The TimeQuest Timing Analyzer does not apply
clock uncertainty to transfers involving the same
physical launch and latch edge (that is, the latch and
launch edges are the same edge of a clock source and
occur at the same time) by default. Such transfers 
typically occur in hold analysis, but may also occur in 
setup analysis with a multicycle value of 0. You can 
use -enable_same_physical_edge option to override this
behavior.

                The values for the -from, -to, and similar options are
either collections or a Tcl list of wildcards used to
create collections of appropriate types. The values
used must follow standard Tcl or TimeQuest-extension
substitution rules. See the help for
use_timequest_style_escaping for details.
Example Usage 
set_clock_uncertainty -setup -rise_from clk1 -fall_to clk2 200ps
Return Value Code Name Code String Return
TCL_OK 0 INFO: Operation successful