Altera SDC and TimeQuest API - Manual (Page 40)

2–30 Chapter 2: SDC and TimeQuest API Package and Commands
sdc
SDC and TimeQuest API Reference Manual © December 2009 Altera Corporation
set_false_path
Usage
set_false_path [-fall_from <names>] [-fall_to <names>] [-from <names>] [-hold]
[-rise_from <names>] [-rise_to <names>] [-setup] [-through <names>] [-to <names>]
Options
-fall_from <names>: Valid source clocks (string patterns are matched using Tcl string
matching)
-fall_to <names>: Valid destination clocks (string patterns are matched using Tcl
string matching)
-from <names>: Valid sources (string patterns are matched using Tcl string matching)
-hold: Specifies the false_path value (applies only to clock hold or removal checks)
-rise_from <names>: Valid source clocks (string patterns are matched using Tcl string
matching)
-rise_to <names>: Valid destination clocks (string patterns are matched using Tcl
string matching)
-setup: Specifies the false_path value (applies only to clock setup or recovery checks)
-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)
Description
Specifies a false-path exception, removing (or cutting) paths from timing analysis.
The -from and -to values are collections of clocks, registers, ports, pins, or cells in the design. If the -from
or -to values are not specified, the collection is converted automatically into [get_keepers *]. It is worth
noting that if the counterpart of the unspecified collection is a clock collection, it is more efficient to
explicitly specify this collection as a clock collection only if the clock collection also generates the desired
assignment.
Applying exceptions between clocks applies the exception from all register or ports driven by the -from
clock to all registers or ports driven by the -to clock. Applying exceptions between a pair of clocks is more
efficient than for specific node to node or node to clock paths.
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 applies to all registers in
the cell or driven by the clock pin.
The -through values are collections of pins or nets in the design. An exception applied through a node in
the design applies only to paths through the specified node.
The -rise_from and -fall_from options can be used in place of the -from destination nodes. The rise or fall
value of the option indicates that the "from" nodes are driven by the rising or falling edge of the clock that
feeds this node, taking into consideration any logical inversions along the clock path. The -from option is
the combination of both rising and falling "from" nodes. If the "from" collection is a clock collection, the
assignment applies to those nodes that are driven by the respective rising or falling clock edge.
The -rise_to and -fall_to options behave similarly to the "from" options described previously. These
assignments restrict the given assignment to only those nodes or clocks that correspond to the specified
rise or fall value, taking into consideration any logical inversions that are along the clock path.