JJin01
New Contributor
New ContributorI want to use external switching clock.. plz help
My design need a external switching clock, which is an input clock that can externally reset its clock rate. I need to constrain this clock, but I don't know how to do it.. ryan scovil' time...
Are you saying that the input clock can be anything between 10 MHz and 300 MHz? If so, you'd probably want to constrain for the fastest clock (replace ext_clk with the name of your top-level clock port:
create_clock -name ext_clk -period 3.3 [get_ports ext_clk]
Then, if it's going through a PLL, just use:
derive_pll_clocks
#iwork4intel
