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Honored Contributor
Honored ContributorImplementing Phase Accumulator in VHDL
Hi, I am currently in the process of designing a Phase Accumulator in VHDL for Altera Cyclone 3 Family. I realise there is an NCO Mega Function in the Altera Library. Can some one explain...
Altera_ForumHonored Contributor
Honored Contributorthe 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.
