section 7 - Index of

Real input FFT based on Glenn Bergland algorithm; Normal order input and normal order output.; Since 56001 does not support bergland addressing, extra instruction cycles are needed; for converting bergland order to normal order. It has been done in the last pass by; looking at the bergtable.; The micro 'bergsincos' generates SIN and COS table with size of points/4, COS in Y, SIN in X; The micro 'bergorder' generates table for address conversion, the size of twiddle factors is half; of FFT output's.; The micro 'norm2berg' converts normal order data to bergland order.; The micro 'rfft-56b' does FFT.; Real input data are split into two parts, the first part is put in X, the second in Y.; Real output data are in X, imaginary output data are in Y.; The bergland table for converting berglang order to normal order is stored in output buffer.; In the last pass the FFT output overwrites this table.; The first real output plus the first imaginary output is DC value of the spectrum.; Note that only DC to Nyquist frequency range is calculated by this algorithm.; After twiddle factors and bergtable are generated, you may overwrite 'bergorder',; 'norm2berg' by 'rfft-56b' for saving P memory.Real input data points641282565121024Performance,------------------------------------------------------------------P memory87Memory (word)X memorypoints/2 (real input) +points/4 (SIN table) +points/2 (real output) +points/2 (bergtable),-------------------------------------------------------------------Clock cycle1686384686561929649776Y memorypOints/2 (imaginary input)points/4 (COS table)points/2 (imaginary output)rfft56bt ident 1,3page 132,60opt nomd,nomex,loc,nocex,muinclude 'bergsincos'include 'bergorder'include 'norm2berg'include 'rfft-56b'Figure B-5 Real Input FFT Based on Glenn Bergland Algorithm (Sheet 1 of 8)