182 lines
7.4 KiB
NASM
182 lines
7.4 KiB
NASM
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/******************************************************************************
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Cfft2_2191.ASM ADSP-2191 Radix-2 DIT Complex FFT
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Performs a radix-2 DIT FFT of length 64 or greater on input data x(n).
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N Real part of normal-ordered complex input stored in DM
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N Imaginary part of normal-ordered complex input stored in PM
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N Real part of fft stored in DM
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N/2 Sin table stored in DM
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N/2 Cos table stored in PM
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Calling Information:
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pm(twid_real[N/2]) - sin(2pi*n/N) table in bitreversed order
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dm(twid_imag[N/2]) - cos(2pi*n/N) table in bitreversed order
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dm(Inputreal[N]) - Real part of complex input array stored in dm
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pm(Inputimag[N]) - Imaginary part of complex input array stored in pm
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Results:
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dm(Refft[N]) - Real FFT results ordered sequentially
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dm(Inputreal[N]) - Imaginary FFT results ordered sequentially
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Benchmarks:
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FFT Length cycles time (us) 160MHz
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---------- ------------- ---------------
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1024 24160 151
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Memory Usage:
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PM code(24-bit) = 92 words
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PM data(24-bit) = N + 2 + N/2 words
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DM data(16-bit) = 2N + 4 + N + 1 words
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******************************************************************************/
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/**********The constants below must be changed for different length FFTs*******
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N = number of points in the FFT, must be a power of 2
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log2N = log2(N)
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Mod_Value = 2^(16-LOG2N)
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Refft_Bitrev = bitrev addr of output real in dm
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Inputreal_Bitrev = bitrev addr of output imag in dm
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******************************************************************************/
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/* Set Constants for N-point FFT */
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#define N 1024
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#define Ndiv2 (N/2)
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#define log2N 10
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#define Mod_Value 64
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#define Refft_Bitrev 0x0001
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#define Inputreal_Bitrev 0x0009
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/* DM data */
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.section/data data1;
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.VAR twid_imag [Ndiv2] = "twid_sin.dat";
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.VAR groups = 1;
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.VAR node_space = Ndiv2;
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/* DM data */
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.section/data seg_buf1;
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.VAR Inputreal [N+2] = "inreal.dat";
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/* DM data */
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.section/data seg_buf2;
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.VAR Refft[N+2];
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/* PM data */
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.section/pm data2;
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.VAR/init24 twid_real [Ndiv2] = "twid_cos.dat";
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.VAR Inputimag [N+2] = "inimag.dat";
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/* PM interrupt vector code */
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.section/pm IVreset;
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JUMP start; NOP; NOP;
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/* Program Code */
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.section/pm program;
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start:
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dmpg2 = page(twid_real); /* Initialize page for PM data */
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M0 = 0;
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L0 = length(twid_imag); /* Initialize twid_imag circular buffer */
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AX1 = twid_imag;
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REG(b0) = AX1; /* Initialize pointer to twid_imag */
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M1 = 1;
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L1 = 0; /* Initialize for modulo addressing */
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M4 = 0;
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L4 = length(twid_real); /* Initialize twid_real circular buffer */
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AX1 = twid_real;
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REG(b4) = AX1; /* Initialize pointer to twid_real */
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M5 = 1;
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L5 = 0; /* Initialize for modulo addressing */
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M6 = -1;
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L6 = 0; /* Initialize for modulo addressing */
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L2 = 0;
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L3 = 0;
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L7 = 0;
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CNTR = log2N -1; /* Initialize Stage Counter */
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DO stage_loop UNTIL CE; /* Compute all stages in FFT */
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I0 = twid_imag; /* I0 --> (-S) of W0 */
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I1 = Inputreal; /* I1 --> x1 in 1st group of stage */
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I2 = Inputreal; /* I2 --> x0 in 1st group of stage */
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I4 = twid_real; /* I4 --> C of W0 */
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I5 = Inputimag; /* I5 --> y1 in 1st group of stage */
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I6 = Inputimag; /* I6 --> y0 in 1st group of stage */
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SI = DM(groups);
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CNTR = SI; /* CNTR = # of groups in stage */
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SR = LSHIFT SI BY 1(LO);
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DM(groups) = SR0;
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SI = DM(node_space); /* SI = node_space modifier */
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M2 =SI;
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M7 =SI;
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MODIFY(I1,M2); /* I1 --> x1 in 1st group of stage */
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MODIFY(I5,M7); /* I5 --> y1 in 1st group of stage */
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DO group_loop UNTIL CE;
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MY0 = PM(I4,M5), MX0 = DM(I1,M0); /* MY0=C, MX0=x1 */
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MR = MX0*MY0(SS), MX1 = PM(I5,M4); /* MR=C*x1,MX1=y1 */
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MY1 = DM(I0,M1); /* MY1 = (-S) */
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CNTR = SI; /* CNTR = butterfly counter */
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DO bfly_loop UNTIL CE;
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MR = MR-MX1*MY1(RND), AY0 = DM(I2,M0); /* MR=x1*C-y1*-S, AY0=x0 */
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AR = MR1+AY0, AX1 = PM(I5,M5); /* AR=x0'=x0+(x1*C-y1*-S) */
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DM(I2,M1) = AR, AR = AY0-MR1; /* DM=x0', AR=x1'=x0-(x1*C-y1*(-S)) */
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MR = MX0*MY1(SS), DM(I1,M1) = AR; /* MR=x1*(-S), DM=x1' */
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MR = MR+MX1*MY0(RND), AY1 = PM(I6,M4), MX0 = DM(I1,M0); /*MR=x1*(-S)+y1*C, AY1=y0, MX0=next x1*/
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AR = MR1+AY1, MX1 = PM(I5,M6); /* AR=y0'=y0+(y1*C+x1*(-S)), MX1= next y1 */
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PM(I6,M5) = AR, AR = AY1-MR1; /* PM=y0', AR=y1'=y0-(y1*C+x1*(-S)) */
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bfly_loop:
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MR = MX0*MY0(SS), PM(I5,M5) = AR; /* PM=y1' */
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MY0 = PM(I5,M7), MX0 = DM(I1,M2);
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group_loop:
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MY0=PM(I6,M7), MX0=DM(I2,M2);
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SR=ASHIFT SI BY -1 (LO);
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stage_loop:
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DM(node_space)=SR0;
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I0 = twid_imag; /* I0 --> (-S) */
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I1 = Inputreal; /* I1 --> x1 */
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I2 = Inputreal; /* I2 --> x0 */
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M2 = 2;
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I3 = Refft_Bitrev; /* Refft bitreversed */
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M3 = Mod_Value; /* Bitreversed modifier */
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I4 = twid_real; /* I4 --> C */
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I5 = Inputimag; /* I5 --> y1 */
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I6 = Inputimag; /* I6 --> y0 */
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M6 = 2;
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MODIFY(I1,M1); /* I1 -->x1 */
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MODIFY(I5,M5); /* I5 -->y1 */
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MY0 = PM(I4,M5), MX0 = DM(I1,M2); /* MY0=C, MX0=x1 */
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MR = MX0*MY0(SS), MX1 = PM(I5,M6); /* MR = C*x1, MX1 = y1 */
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MY1 = DM(I0,M1); /* MY1 = (-S) */
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CNTR = Ndiv2;
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DO last_loop UNTIL CE;
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MR = MR-MX1*MY1(RND), AY0 = DM(I2,M2); /* MR=x1*C-y1*(-S), AY0=x0 */
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AR = MR1+AY0, AY1 = PM(I6,M4); /* AR=x0'=x0+(x1*C-y1*(-S)), AY1=y0 */
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ENA BIT_REV;
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DM(I3,M3) = AR, AR = AY0-MR1; /* Read real data */
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MR = MX0*MY1(SS), DM(I3,M3) = AR; /* Place in sequential order(using bit-reversal) */
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DIS BIT_REV;
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MR = MR+MX1*MY0(RND), MY0 = PM(I4,M5), MX0 = DM(I1,M2);
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AR = MR1+AY1, MX1 = PM(I5,M6); /* AR=y0'=y0+(y1*C+x1*(-S)), MX1= next y1 */
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PM(I6,M5) = AR, AR = AY1-MR1; /* PM=y0', AR=y1'=y0-(y1*C+x1*(-S)) */
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MY1 = DM(I0,M1); /* MY1 = (-S) */
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last_loop:
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MR = MX0*MY0(SS), PM(I6,M5) = AR; /*PM=y1' */
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I3 = Inputreal_Bitrev;
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M3 = Mod_Value; /* Bitreversed modifier */
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I5 = Inputimag;
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ENA BIT_REV;
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CNTR = N;
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DO bit_rev_imag UNTIL CE;
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AX0 = PM(I5,M5); /* Read imaginary data */
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bit_rev_imag: DM(I3,M3) = AX0; /* Place in sequential order */
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DIS BIT_REV;
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looping: JUMP looping;
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