Altera SDC and TimeQuest API - Manual (Page 49)

Chapter 2: SDC and TimeQuest API Package and Commands 2–39
sdc
© December 2009 Altera Corporation SDC and TimeQuest API Reference Manual
set_multicycle_path
Usage
set_multicycle_path [-end] [-fall_from ] [-fall_to ] [-from ]
[-hold] [-rise_from ] [-rise_to ] [-setup] [-start] [-through ]
[-to ]
Options
-end: Specifies that the multicycle is relative to the destination clock waveform
(default)
-fall_from : Valid source clocks (string patterns are matched using Tcl string
matching)
-fall_to : Valid destination clocks (string patterns are matched using Tcl
string matching)
-from : Valid sources (string patterns are matched using Tcl string matching)
-hold: Specifies that the multicycle value applies to clock hold or removal checks
-rise_from : Valid source clocks (string patterns are matched using Tcl string
matching)
-rise_to : Valid destination clocks (string patterns are matched using Tcl
string matching)
-setup: Specifies that the multicycle value applies to clock setup or recovery checks
(default)
-start: Specifies that the multicycle is relative to the source clock waveform
-through : Valid through nodes (string patterns are matched using Tcl string
matching)
-to : Valid destinations (string patterns are matched using Tcl string matching)
: Number of clock cycles
Description
Specifies a multicycle exception for a given set of paths.
Multicycles can be specified relative to the source clock (-start) or destination clock (-end). This is useful
when the source clock and destination clock are operating at different frequencies. For example, if the
source clock is twice as fast (half period) as the destination clock, a -start multicycle of 2 is usually
required.
Hold multicycles (-hold) are computed relative to setup multicycles (-setup). The value of the hold
multicycle represents the number clock edges away from the default hold multicycle. The default hold
multicycle value is 0.
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 but 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. Also, applying exceptions between a pair of clocks is
more efficient than for specific node to node or node to clock paths.