What does set_clock_groups -asynchronous -group {clk1} do when there is no other group listed?

[JArnw]

I see a constraint set_clock_groups -asynchronous -group {clk1}

no other clock group in the statement. What is this constraint actually doing?

[sstrell]

It means that all cross-domain paths to and from anything clocked by clk1 are cut and not analyzed by the timing analyzer. Basically the clock domain is isolated from all other clock domains in the design.

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