NCO Sine output

I was expecting mod input to be signed but it seems not.

assuming accumulator resolution of 20 bits and mod_i resolution of 16 bits then and according to doc:

fo = clk*inc/2^20 (hence inc = fo*2^20/clk)

f(fm) = clk*mod_i/2^16 (hence mod_i = f(fm)*2^16/clk)

what f(fm) means only God and altera editor knows.. I think they mean increment from fo.

I think you can easily test that and tell us.