Implementing Phase Accumulator in VHDL

the NCO is based on 3 resolutions:

- accumulator resolution. Many designers choose 32 bits as it is cheap. This affects the addition result ofcourse. a 32 bit modulo adder keeps building up the result more correctly but never exactly.

-phase resolution: select a number of accumulator MSBs to be used for addressing your lut. You don't want a 2^32 data points in your lut. It is too much. Ignore the LSBs of accumulator for addressing.

-amplitude resolution: number of bits per data point.

The lut is just one exact cycle of sine/cosine

it is also possible to compute phase points from adjacent sine/cosine points resulting in virtual large LUT.