Generating higher frequency sine waves from 5MHz RAM

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I'm not too familiar with the NCO approach, but I would like to keep my Vpp to be 1. In MATLAB I had my amplitude to be 0.5. Correct me if I'm wrong, but the clocking into my modules are what my sampling frequency is. It would have to match the MATLAB implemented into a MIF file and in my Verilog design. So by changing my input clock from 250MHz to 500MHz through PLL, my sampling frequency will give me double the samples (100 samples for 5MHz at 250MHz sampling frequency), raising the threshold of address manipulation before undersampling.

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You are following the equation: Fo = Fs/samples per cycle

That is correct and you want to change Fo by changing Fs. You can but in most cases we change samples per cycle and keep Fs.

just instantiate an nco core. You don't need to worry about how it works internally but you will input into it increment value for your target Fo.