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Ixiasoft
Clock Multiplexing
With clock multiplexing, you can select from two or more clocks with the create_clock and set_clock_groups constraints.
Figure 7. Constraints for a Typical 2:1 Clock Multiplexer
Clock Multiplexer Constraints
#Create the first input clock clkA to the mux
create_clock -period 10.000 -name clkA [get_ports {clkA}]
#Create the second input clock clkB to the mux
create_clock -period 20.000 -name clkB [get_ports {clkB}]
#Cut paths between clkA and clkB
set_clock_groups -exclusive -group {clkA} -group {clkB}