Altera SDC and TimeQuest API - Manual (Page 68)

2–58 Chapter 2: SDC and TimeQuest API Package and Commands
sdc_ext
SDC and TimeQuest API Reference Manual © December 2009 Altera Corporation
set_max_skew
Usage
set_max_skew [-exclude <Tcl list>] [-fall_from_clock <names>] [-fall_to_clock <names>]
[-from <names>] [-from_clock <names>] [-include <Tcl list>] [-rise_from_clock <names>]
[-rise_to_clock <names>] [-through <names>] [-to <names>] [-to_clock <names>] <skew>
Options
-exclude <Tcl list>: A Tcl list of parameters to exclude during skew analysis. This list
can include 1 or more of the following: utsu, uth, utco, from_clock, to_clock,
clock_uncertainty, input_delay, output_delay
-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)
-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)
-include <Tcl list>: Tcl list of parameters to include during skew analysis. This list
can include 1 or more of the following: utsu, uth, utco, from_clock, to_clock,
clock_uncertainty, input_delay, output_delay
-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)
-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)
<skew>: Required skew
Description
Use the set_max_skew constraint to perform maximum allowable skew analysis between sets of registers
or ports. In order to constrain skew across multiple paths, all such paths must be defined within a single
set_max_skew constraint. set_max_skew timing constraint is not affected by set_max_delay,
set_min_delay and set_multicycle_path but it does obey set_false_path and set_clock_groups.
Legal values for the -from and -to options are collections of clocks, registers, ports, pins, nets, cells or
partitions in a design.
Applying maximum skew constraints between clocks applies the constraint from all register or ports
driven by the clock specified with the -from option to all registers or ports driven by the clock specified
with the -to option.
If pin names or collections are used, the -from value must be a clock pin and the -to value must be any
non-clock input pin to a register. Assignments from clock pins or to and from cells apply to all registers
contained in the cell or driven by the clock pin. Similarly, -to and -from partition specifications apply to all
registers in the specified partition.