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You surely won't see a LED driven by clkout flashing, because it's only active for one clock cycle. But the warning reveals, that c1hz isn't your design top entity, so it's not clear at all, how the c1hz ports are wired.
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Thanks for your reply FvM!
i do see your point about a flashing led, in order to make it flash, would i have to change the 2nd if statement condition to if (cnt < '12587500') rather than if (cnt = '12587500')?
i'm not sure why c1hz isn't my top entity, all i did was create a new project and a new vhdl file and pasted the code in, and set the pins i wanted to use.